Merge branch 'master' into master

This commit is contained in:
程序员Carl
2022-02-18 10:07:32 +08:00
committed by GitHub
33 changed files with 1315 additions and 226 deletions

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@ -5,10 +5,11 @@
> 1. **介绍**:本项目是一套完整的刷题计划,旨在帮助大家少走弯路,循序渐进学算法,[关注作者](#关于作者) > 1. **介绍**:本项目是一套完整的刷题计划,旨在帮助大家少走弯路,循序渐进学算法,[关注作者](#关于作者)
> 2. **PDF版本** [「代码随想录」算法精讲 PDF 版本](https://programmercarl.com/other/algo_pdf.html) 。 > 2. **PDF版本** [「代码随想录」算法精讲 PDF 版本](https://programmercarl.com/other/algo_pdf.html) 。
> 3. **刷题顺序** README已经将刷题顺序排好了按照顺序一道一道刷就可以。 > 3. **最强八股文:**[代码随想录知识星球精华PDF](https://www.programmercarl.com/other/kstar_baguwen.html)
> 4. **学习社区** : 一起学习打卡/面试技巧/如何选择offer/大厂内推/职场规则/简历修改/技术分享/程序人生。欢迎加入[「代码随想录」知识星球](https://programmercarl.com/other/kstar.html) > 4. **刷题顺序** README已经将刷题顺序排好了按照顺序一道一道刷就可以
> 5. **提交代码**本项目统一使用C++语言进行讲解但已经有Java、Python、Go、JavaScript等等多语言版本感谢[这里的每一位贡献者](https://github.com/youngyangyang04/leetcode-master/graphs/contributors),如果你也想贡献代码点亮你的头像,[点击这里](https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A)了解提交代码的方式 > 5. **学习社区** : 一起学习打卡/面试技巧/如何选择offer/大厂内推/职场规则/简历修改/技术分享/程序人生。欢迎加入[「代码随想录」知识星球](https://programmercarl.com/other/kstar.html)
> 6. **转载须知** :以下所有文章皆为我([程序员Carl](https://github.com/youngyangyang04))的原创。引用本项目文章请注明出处,发现恶意抄袭或搬运,会动用法律武器维护自己的权益。让我们一起维护一个良好的技术创作环境! > 6. **提交代码**本项目统一使用C++语言进行讲解但已经有Java、Python、Go、JavaScript等等多语言版本感谢[这里的每一位贡献者](https://github.com/youngyangyang04/leetcode-master/graphs/contributors),如果你也想贡献代码点亮你的头像,[点击这里](https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A)了解提交代码的方式。
> 7. **转载须知** :以下所有文章皆为我([程序员Carl](https://github.com/youngyangyang04))的原创。引用本项目文章请注明出处,发现恶意抄袭或搬运,会动用法律武器维护自己的权益。让我们一起维护一个良好的技术创作环境!
<p align="center"> <p align="center">
<a href="programmercarl.com" target="_blank"> <a href="programmercarl.com" target="_blank">

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@ -142,6 +142,7 @@ public:
### Java ### Java
```Java ```Java
// 版本一
class Solution { class Solution {
public int jump(int[] nums) { public int jump(int[] nums) {
if (nums == null || nums.length == 0 || nums.length == 1) { if (nums == null || nums.length == 0 || nums.length == 1) {
@ -172,7 +173,30 @@ class Solution {
} }
``` ```
```java
// 版本二
class Solution {
public int jump(int[] nums) {
int result = 0;
// 当前覆盖的最远距离下标
int end = 0;
// 下一步覆盖的最远距离下标
int temp = 0;
for (int i = 0; i <= end && end < nums.length - 1; ++i) {
temp = Math.max(temp, i + nums[i]);
// 可达位置的改变次数就是跳跃次数
if (i == end) {
end = temp;
result++;
}
}
return result;
}
}
```
### Python ### Python
```python ```python
class Solution: class Solution:
def jump(self, nums: List[int]) -> int: def jump(self, nums: List[int]) -> int:

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@ -4,7 +4,7 @@
</a> </a>
<p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>,贡献其他语言版本的代码,拥抱开源,让更多学习算法的小伙伴们收益!</strong></p> <p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>,贡献其他语言版本的代码,拥抱开源,让更多学习算法的小伙伴们收益!</strong></p>
## 63. 不同路径 II # 63. 不同路径 II
[力扣题目链接](https://leetcode-cn.com/problems/unique-paths-ii/) [力扣题目链接](https://leetcode-cn.com/problems/unique-paths-ii/)
@ -22,23 +22,22 @@
![](https://img-blog.csdnimg.cn/20210111204939971.png) ![](https://img-blog.csdnimg.cn/20210111204939971.png)
输入obstacleGrid = [[0,0,0],[0,1,0],[0,0,0]] * 输入obstacleGrid = [[0,0,0],[0,1,0],[0,0,0]]
输出2 * 输出2
解释: 解释:
3x3 网格的正中间有一个障碍物。 * 3x3 网格的正中间有一个障碍物。
从左上角到右下角一共有 2 条不同的路径: * 从左上角到右下角一共有 2 条不同的路径:
1. 向右 -> 向右 -> 向下 -> 向下 1. 向右 -> 向右 -> 向下 -> 向下
2. 向下 -> 向下 -> 向右 -> 向右 2. 向下 -> 向下 -> 向右 -> 向右
示例 2 示例 2
![](https://img-blog.csdnimg.cn/20210111205857918.png) ![](https://img-blog.csdnimg.cn/20210111205857918.png)
输入obstacleGrid = [[0,1],[0,0]] * 输入obstacleGrid = [[0,1],[0,0]]
输出1 * 输出1
提示: 提示:
* m == obstacleGrid.length * m == obstacleGrid.length
* n == obstacleGrid[i].length * n == obstacleGrid[i].length
* 1 <= m, n <= 100 * 1 <= m, n <= 100
@ -171,7 +170,7 @@ public:
## 其他语言版本 ## 其他语言版本
Java ### Java
```java ```java
class Solution { class Solution {
@ -199,7 +198,7 @@ class Solution {
``` ```
Python ### Python
```python ```python
class Solution: class Solution:
@ -262,7 +261,7 @@ class Solution:
``` ```
Go ### Go
```go ```go
func uniquePathsWithObstacles(obstacleGrid [][]int) int { func uniquePathsWithObstacles(obstacleGrid [][]int) int {
@ -295,8 +294,8 @@ func uniquePathsWithObstacles(obstacleGrid [][]int) int {
``` ```
Javascript ### Javascript
``` Javascript ```Javascript
var uniquePathsWithObstacles = function(obstacleGrid) { var uniquePathsWithObstacles = function(obstacleGrid) {
const m = obstacleGrid.length const m = obstacleGrid.length
const n = obstacleGrid[0].length const n = obstacleGrid[0].length

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@ -4,7 +4,7 @@
</a> </a>
<p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>,贡献其他语言版本的代码,拥抱开源,让更多学习算法的小伙伴们收益!</strong></p> <p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>,贡献其他语言版本的代码,拥抱开源,让更多学习算法的小伙伴们收益!</strong></p>
## 96.不同的二叉搜索树 # 96.不同的二叉搜索树
[力扣题目链接](https://leetcode-cn.com/problems/unique-binary-search-trees/) [力扣题目链接](https://leetcode-cn.com/problems/unique-binary-search-trees/)
@ -163,7 +163,7 @@ public:
## 其他语言版本 ## 其他语言版本
Java ### Java
```Java ```Java
class Solution { class Solution {
public int numTrees(int n) { public int numTrees(int n) {
@ -184,7 +184,7 @@ class Solution {
} }
``` ```
Python ### Python
```python ```python
class Solution: class Solution:
def numTrees(self, n: int) -> int: def numTrees(self, n: int) -> int:
@ -196,7 +196,7 @@ class Solution:
return dp[-1] return dp[-1]
``` ```
Go ### Go
```Go ```Go
func numTrees(n int)int{ func numTrees(n int)int{
dp:=make([]int,n+1) dp:=make([]int,n+1)
@ -210,7 +210,7 @@ func numTrees(n int)int{
} }
``` ```
Javascript ### Javascript
```Javascript ```Javascript
const numTrees =(n) => { const numTrees =(n) => {
let dp = new Array(n+1).fill(0); let dp = new Array(n+1).fill(0);

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@ -574,6 +574,75 @@ var isSymmetric = function(root) {
}; };
``` ```
## TypeScript
> 递归法
```typescript
function isSymmetric(root: TreeNode | null): boolean {
function recur(node1: TreeNode | null, node2: TreeNode | null): boolean {
if (node1 === null && node2 === null) return true;
if (node1 === null || node2 === null) return false;
if (node1.val !== node2.val) return false
let isSym1: boolean = recur(node1.left, node2.right);
let isSym2: boolean = recur(node1.right, node2.left);
return isSym1 && isSym2
}
if (root === null) return true;
return recur(root.left, root.right);
};
```
> 迭代法
```typescript
// 迭代法(队列)
function isSymmetric(root: TreeNode | null): boolean {
let helperQueue: (TreeNode | null)[] = [];
let tempNode1: TreeNode | null,
tempNode2: TreeNode | null;
if (root !== null) {
helperQueue.push(root.left);
helperQueue.push(root.right);
}
while (helperQueue.length > 0) {
tempNode1 = helperQueue.shift()!;
tempNode2 = helperQueue.shift()!;
if (tempNode1 === null && tempNode2 === null) continue;
if (tempNode1 === null || tempNode2 === null) return false;
if (tempNode1.val !== tempNode2.val) return false;
helperQueue.push(tempNode1.left);
helperQueue.push(tempNode2.right);
helperQueue.push(tempNode1.right);
helperQueue.push(tempNode2.left);
}
return true;
}
// 迭代法(栈)
function isSymmetric(root: TreeNode | null): boolean {
let helperStack: (TreeNode | null)[] = [];
let tempNode1: TreeNode | null,
tempNode2: TreeNode | null;
if (root !== null) {
helperStack.push(root.left);
helperStack.push(root.right);
}
while (helperStack.length > 0) {
tempNode1 = helperStack.pop()!;
tempNode2 = helperStack.pop()!;
if (tempNode1 === null && tempNode2 === null) continue;
if (tempNode1 === null || tempNode2 === null) return false;
if (tempNode1.val !== tempNode2.val) return false;
helperStack.push(tempNode1.left);
helperStack.push(tempNode2.right);
helperStack.push(tempNode1.right);
helperStack.push(tempNode2.left);
}
return true;
};
```
## Swift: ## Swift:
> 递归 > 递归

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@ -246,7 +246,35 @@ var levelOrder = function(root) {
``` ```
TypeScript
```typescript
function levelOrder(root: TreeNode | null): number[][] {
let helperQueue: TreeNode[] = [];
let res: number[][] = [];
let tempArr: number[] = [];
if (root !== null) helperQueue.push(root);
let curNode: TreeNode;
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
curNode = helperQueue.shift()!;
tempArr.push(curNode.val);
if (curNode.left !== null) {
helperQueue.push(curNode.left);
}
if (curNode.right !== null) {
helperQueue.push(curNode.right);
}
}
res.push(tempArr);
tempArr = [];
}
return res;
};
```
Swift: Swift:
```swift ```swift
func levelOrder(_ root: TreeNode?) -> [[Int]] { func levelOrder(_ root: TreeNode?) -> [[Int]] {
var res = [[Int]]() var res = [[Int]]()
@ -454,7 +482,31 @@ var levelOrderBottom = function(root) {
}; };
``` ```
TypeScript:
```typescript
function levelOrderBottom(root: TreeNode | null): number[][] {
let helperQueue: TreeNode[] = [];
let resArr: number[][] = [];
let tempArr: number[] = [];
let tempNode: TreeNode;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
tempNode = helperQueue.shift()!;
tempArr.push(tempNode.val);
if (tempNode.left !== null) helperQueue.push(tempNode.left);
if (tempNode.right !== null) helperQueue.push(tempNode.right);
}
resArr.push(tempArr);
tempArr = [];
}
return resArr.reverse();
};
```
Swift: Swift:
```swift ```swift
func levelOrderBottom(_ root: TreeNode?) -> [[Int]] { func levelOrderBottom(_ root: TreeNode?) -> [[Int]] {
var res = [[Int]]() var res = [[Int]]()
@ -657,7 +709,28 @@ var rightSideView = function(root) {
}; };
``` ```
TypeScript
```typescript
function rightSideView(root: TreeNode | null): number[] {
let helperQueue: TreeNode[] = [];
let resArr: number[] = [];
let tempNode: TreeNode;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
tempNode = helperQueue.shift()!;
if (i === length - 1) resArr.push(tempNode.val);
if (tempNode.left !== null) helperQueue.push(tempNode.left);
if (tempNode.right !== null) helperQueue.push(tempNode.right);
}
}
return resArr;
};
```
Swift: Swift:
```swift ```swift
func rightSideView(_ root: TreeNode?) -> [Int] { func rightSideView(_ root: TreeNode?) -> [Int] {
var res = [Int]() var res = [Int]()
@ -868,7 +941,32 @@ var averageOfLevels = function(root) {
}; };
``` ```
TypeScript
```typescript
function averageOfLevels(root: TreeNode | null): number[] {
let helperQueue: TreeNode[] = [];
let resArr: number[] = [];
let total: number = 0;
let tempNode: TreeNode;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
let length = helperQueue.length;
for (let i = 0; i < length; i++) {
tempNode = helperQueue.shift()!;
total += tempNode.val;
if (tempNode.left) helperQueue.push(tempNode.left);
if (tempNode.right) helperQueue.push(tempNode.right);
}
resArr.push(total / length);
total = 0;
}
return resArr;
};
```
Swift: Swift:
```swift ```swift
func averageOfLevels(_ root: TreeNode?) -> [Double] { func averageOfLevels(_ root: TreeNode?) -> [Double] {
var res = [Double]() var res = [Double]()
@ -1092,7 +1190,30 @@ var levelOrder = function(root) {
}; };
``` ```
TypeScript:
```typescript
function levelOrder(root: Node | null): number[][] {
let helperQueue: Node[] = [];
let resArr: number[][] = [];
let tempArr: number[] = [];
if (root !== null) helperQueue.push(root);
let curNode: Node;
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
curNode = helperQueue.shift()!;
tempArr.push(curNode.val);
helperQueue.push(...curNode.children);
}
resArr.push(tempArr);
tempArr = [];
}
return resArr;
};
```
Swift: Swift:
```swift ```swift
func levelOrder(_ root: Node?) -> [[Int]] { func levelOrder(_ root: Node?) -> [[Int]] {
var res = [[Int]]() var res = [[Int]]()
@ -1272,7 +1393,34 @@ var largestValues = function(root) {
}; };
``` ```
TypeScript:
```typescript
function largestValues(root: TreeNode | null): number[] {
let helperQueue: TreeNode[] = [];
let resArr: number[] = [];
let tempNode: TreeNode;
let max: number = 0;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
tempNode = helperQueue.shift()!;
if (i === 0) {
max = tempNode.val;
} else {
max = max > tempNode.val ? max : tempNode.val;
}
if (tempNode.left) helperQueue.push(tempNode.left);
if (tempNode.right) helperQueue.push(tempNode.right);
}
resArr.push(max);
}
return resArr;
};
```
Swift: Swift:
```swift ```swift
func largestValues(_ root: TreeNode?) -> [Int] { func largestValues(_ root: TreeNode?) -> [Int] {
var res = [Int]() var res = [Int]()
@ -1463,6 +1611,31 @@ var connect = function(root) {
}; };
``` ```
TypeScript:
```typescript
function connect(root: Node | null): Node | null {
let helperQueue: Node[] = [];
let preNode: Node, curNode: Node;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
if (i === 0) {
preNode = helperQueue.shift()!;
} else {
curNode = helperQueue.shift()!;
preNode.next = curNode;
preNode = curNode;
}
if (preNode.left) helperQueue.push(preNode.left);
if (preNode.right) helperQueue.push(preNode.right);
}
preNode.next = null;
}
return root;
};
```
go: go:
```GO ```GO
@ -1689,6 +1862,31 @@ var connect = function(root) {
return root; return root;
}; };
``` ```
TypeScript:
```typescript
function connect(root: Node | null): Node | null {
let helperQueue: Node[] = [];
let preNode: Node, curNode: Node;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
if (i === 0) {
preNode = helperQueue.shift()!;
} else {
curNode = helperQueue.shift()!;
preNode.next = curNode;
preNode = curNode;
}
if (preNode.left) helperQueue.push(preNode.left);
if (preNode.right) helperQueue.push(preNode.right);
}
preNode.next = null;
}
return root;
};
```
go: go:
```GO ```GO
@ -1933,7 +2131,28 @@ var maxDepth = function(root) {
}; };
``` ```
TypeScript:
```typescript
function maxDepth(root: TreeNode | null): number {
let helperQueue: TreeNode[] = [];
let resDepth: number = 0;
let tempNode: TreeNode;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
resDepth++;
for (let i = 0, length = helperQueue.length; i < length; i++) {
tempNode = helperQueue.shift()!;
if (tempNode.left) helperQueue.push(tempNode.left);
if (tempNode.right) helperQueue.push(tempNode.right);
}
}
return resDepth;
};
```
Swift: Swift:
```swift ```swift
func maxDepth(_ root: TreeNode?) -> Int { func maxDepth(_ root: TreeNode?) -> Int {
guard let root = root else { guard let root = root else {
@ -2130,7 +2349,29 @@ var minDepth = function(root) {
}; };
``` ```
TypeScript:
```typescript
function minDepth(root: TreeNode | null): number {
let helperQueue: TreeNode[] = [];
let resMin: number = 0;
let tempNode: TreeNode;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
resMin++;
for (let i = 0, length = helperQueue.length; i < length; i++) {
tempNode = helperQueue.shift()!;
if (tempNode.left === null && tempNode.right === null) return resMin;
if (tempNode.left !== null) helperQueue.push(tempNode.left);
if (tempNode.right !== null) helperQueue.push(tempNode.right);
}
}
return resMin;
};
```
Swift Swift
```swift ```swift
func minDepth(_ root: TreeNode?) -> Int { func minDepth(_ root: TreeNode?) -> Int {
guard let root = root else { guard let root = root else {

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@ -598,7 +598,81 @@ var maxDepth = function(root) {
}; };
``` ```
## TypeScript
> 二叉树的最大深度:
```typescript
// 后续遍历(自下而上)
function maxDepth(root: TreeNode | null): number {
if (root === null) return 0;
return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
};
// 前序遍历(自上而下)
function maxDepth(root: TreeNode | null): number {
function recur(node: TreeNode | null, count: number) {
if (node === null) {
resMax = resMax > count ? resMax : count;
return;
}
recur(node.left, count + 1);
recur(node.right, count + 1);
}
let resMax: number = 0;
let count: number = 0;
recur(root, count);
return resMax;
};
// 层序遍历(迭代法)
function maxDepth(root: TreeNode | null): number {
let helperQueue: TreeNode[] = [];
let resDepth: number = 0;
let tempNode: TreeNode;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
resDepth++;
for (let i = 0, length = helperQueue.length; i < length; i++) {
tempNode = helperQueue.shift()!;
if (tempNode.left) helperQueue.push(tempNode.left);
if (tempNode.right) helperQueue.push(tempNode.right);
}
}
return resDepth;
};
```
> N叉树的最大深度
```typescript
// 后续遍历(自下而上)
function maxDepth(root: TreeNode | null): number {
if (root === null) return 0;
return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
};
// 前序遍历(自上而下)
function maxDepth(root: TreeNode | null): number {
function recur(node: TreeNode | null, count: number) {
if (node === null) {
resMax = resMax > count ? resMax : count;
return;
}
recur(node.left, count + 1);
recur(node.right, count + 1);
}
let resMax: number = 0;
let count: number = 0;
recur(root, count);
return resMax;
};
```
## C ## C
二叉树最大深度递归 二叉树最大深度递归
```c ```c
int maxDepth(struct TreeNode* root){ int maxDepth(struct TreeNode* root){

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@ -670,7 +670,26 @@ var isBalanced = function (root) {
}; };
``` ```
## TypeScript
```typescript
// 递归法
function isBalanced(root: TreeNode | null): boolean {
function getDepth(root: TreeNode | null): number {
if (root === null) return 0;
let leftDepth: number = getDepth(root.left);
if (leftDepth === -1) return -1;
let rightDepth: number = getDepth(root.right);
if (rightDepth === -1) return -1;
if (Math.abs(leftDepth - rightDepth) > 1) return -1;
return 1 + Math.max(leftDepth, rightDepth);
}
return getDepth(root) !== -1;
};
```
## C ## C
递归法: 递归法:
```c ```c
int getDepth(struct TreeNode* node) { int getDepth(struct TreeNode* node) {

View File

@ -404,6 +404,44 @@ var minDepth = function(root) {
}; };
``` ```
## TypeScript
> 递归法
```typescript
function minDepth(root: TreeNode | null): number {
if (root === null) return 0;
if (root.left !== null && root.right === null) {
return 1 + minDepth(root.left);
}
if (root.left === null && root.right !== null) {
return 1 + minDepth(root.right);
}
return 1 + Math.min(minDepth(root.left), minDepth(root.right));
}
```
> 迭代法
```typescript
function minDepth(root: TreeNode | null): number {
let helperQueue: TreeNode[] = [];
let resMin: number = 0;
let tempNode: TreeNode;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
resMin++;
for (let i = 0, length = helperQueue.length; i < length; i++) {
tempNode = helperQueue.shift()!;
if (tempNode.left === null && tempNode.right === null) return resMin;
if (tempNode.left !== null) helperQueue.push(tempNode.left);
if (tempNode.right !== null) helperQueue.push(tempNode.right);
}
}
return resMin;
};
```
## Swift ## Swift
> 递归 > 递归

View File

@ -531,82 +531,63 @@ class solution:
```go ```go
//递归法 //递归法
/** /**
* definition for a binary tree node. * Definition for a binary tree node.
* type treenode struct { * type TreeNode struct {
* val int * Val int
* left *treenode * Left *TreeNode
* right *treenode * Right *TreeNode
* } * }
*/ */
func haspathsum(root *treenode, targetsum int) bool { func hasPathSum(root *TreeNode, targetSum int) bool {
var flage bool //找没找到的标志 if root == nil {
if root==nil{ return false
return flage
} }
pathsum(root,0,targetsum,&flage)
return flage targetSum -= root.Val // 将targetSum在遍历每层的时候都减去本层节点的值
} if root.Left == nil && root.Right == nil && targetSum == 0 { // 如果剩余的targetSum为0, 则正好就是符合的结果
func pathsum(root *treenode, sum int,targetsum int,flage *bool){ return true
sum+=root.val
if root.left==nil&&root.right==nil&&sum==targetsum{
*flage=true
return
}
if root.left!=nil&&!(*flage){//左节点不为空且还没找到
pathsum(root.left,sum,targetsum,flage)
}
if root.right!=nil&&!(*flage){//右节点不为空且没找到
pathsum(root.right,sum,targetsum,flage)
} }
return hasPathSum(root.Left, targetSum) || hasPathSum(root.Right, targetSum) // 否则递归找
} }
``` ```
113 递归法 113. 路径总和 II
```go ```go
/** /**
* definition for a binary tree node. * Definition for a binary tree node.
* type treenode struct { * type TreeNode struct {
* val int * Val int
* left *treenode * Left *TreeNode
* right *treenode * Right *TreeNode
* } * }
*/ */
func pathsum(root *treenode, targetsum int) [][]int { func pathSum(root *TreeNode, targetSum int) [][]int {
var result [][]int//最终结果 result := make([][]int, 0)
if root==nil{ traverse(root, &result, new([]int), targetSum)
return result
}
var sumnodes []int//经过路径的节点集合
haspathsum(root,&sumnodes,targetsum,&result)
return result return result
} }
func haspathsum(root *treenode,sumnodes *[]int,targetsum int,result *[][]int){
*sumnodes=append(*sumnodes,root.val) func traverse(node *TreeNode, result *[][]int, currPath *[]int, targetSum int) {
if root.left==nil&&root.right==nil{//叶子节点 if node == nil { // 这个判空也可以挪到递归遍历左右子树时去判断
fmt.println(*sumnodes) return
var sum int
var number int
for k,v:=range *sumnodes{//求该路径节点的和
sum+=v
number=k
}
tempnodes:=make([]int,number+1)//新的nodes接受指针里的值防止最终指针里的值发生变动导致最后的结果都是最后一个sumnodes的值
for k,v:=range *sumnodes{
tempnodes[k]=v
}
if sum==targetsum{
*result=append(*result,tempnodes)
}
} }
if root.left!=nil{
haspathsum(root.left,sumnodes,targetsum,result) targetSum -= node.Val // 将targetSum在遍历每层的时候都减去本层节点的值
*sumnodes=(*sumnodes)[:len(*sumnodes)-1]//回溯 *currPath = append(*currPath, node.Val) // 把当前节点放到路径记录里
}
if root.right!=nil{ if node.Left == nil && node.Right == nil && targetSum == 0 { // 如果剩余的targetSum为0, 则正好就是符合的结果
haspathsum(root.right,sumnodes,targetsum,result) // 不能直接将currPath放到result里面, 因为currPath是共享的, 每次遍历子树时都会被修改
*sumnodes=(*sumnodes)[:len(*sumnodes)-1]//回溯 pathCopy := make([]int, len(*currPath))
for i, element := range *currPath {
pathCopy[i] = element
}
*result = append(*result, pathCopy) // 将副本放到结果集里
} }
traverse(node.Left, result, currPath, targetSum)
traverse(node.Right, result, currPath, targetSum)
*currPath = (*currPath)[:len(*currPath)-1] // 当前节点遍历完成, 从路径记录里删除掉
} }
``` ```

View File

@ -248,6 +248,36 @@ class Solution {
return valid[s.length()]; return valid[s.length()];
} }
} }
// 回溯法+记忆化
class Solution {
public boolean wordBreak(String s, List<String> wordDict) {
Set<String> wordDictSet = new HashSet(wordDict);
int[] memory = new int[s.length()];
return backTrack(s, wordDictSet, 0, memory);
}
public boolean backTrack(String s, Set<String> wordDictSet, int startIndex, int[] memory) {
// 结束条件
if (startIndex >= s.length()) {
return true;
}
if (memory[startIndex] != 0) {
// 此处认为memory[i] = 1 表示可以拼出i 及以后的字符子串, memory[i] = -1 表示不能
return memory[startIndex] == 1 ? true : false;
}
for (int i = startIndex; i < s.length(); ++i) {
// 处理 递归 回溯 循环不变量:[startIndex, i + 1)
String word = s.substring(startIndex, i + 1);
if (wordDictSet.contains(word) && backTrack(s, wordDictSet, i + 1, memory)) {
memory[startIndex] = 1;
return true;
}
}
memory[startIndex] = -1;
return false;
}
}
``` ```
Python Python

View File

@ -210,6 +210,71 @@ var evalRPN = function(tokens) {
}; };
``` ```
TypeScript
普通版:
```typescript
function evalRPN(tokens: string[]): number {
let helperStack: number[] = [];
let temp: number;
let i: number = 0;
while (i < tokens.length) {
let t: string = tokens[i];
switch (t) {
case '+':
temp = helperStack.pop()! + helperStack.pop()!;
helperStack.push(temp);
break;
case '-':
temp = helperStack.pop()!;
temp = helperStack.pop()! - temp;
helperStack.push(temp);
break;
case '*':
temp = helperStack.pop()! * helperStack.pop()!;
helperStack.push(temp);
break;
case '/':
temp = helperStack.pop()!;
temp = Math.trunc(helperStack.pop()! / temp);
helperStack.push(temp);
break;
default:
helperStack.push(Number(t));
break;
}
i++;
}
return helperStack.pop()!;
};
```
优化版:
```typescript
function evalRPN(tokens: string[]): number {
const helperStack: number[] = [];
const operatorMap: Map<string, (a: number, b: number) => number> = new Map([
['+', (a, b) => a + b],
['-', (a, b) => a - b],
['/', (a, b) => Math.trunc(a / b)],
['*', (a, b) => a * b],
]);
let a: number, b: number;
for (let t of tokens) {
if (operatorMap.has(t)) {
b = helperStack.pop()!;
a = helperStack.pop()!;
helperStack.push(operatorMap.get(t)!(a, b));
} else {
helperStack.push(Number(t));
}
}
return helperStack.pop()!;
};
```
python3 python3
```python ```python

View File

@ -447,7 +447,63 @@ var countNodes = function(root) {
}; };
``` ```
## TypeScrpt:
> 递归法
```typescript
function countNodes(root: TreeNode | null): number {
if (root === null) return 0;
return 1 + countNodes(root.left) + countNodes(root.right);
};
```
> 迭代法
```typescript
function countNodes(root: TreeNode | null): number {
let helperQueue: TreeNode[] = [];
let resCount: number = 0;
let tempNode: TreeNode;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
tempNode = helperQueue.shift()!;
resCount++;
if (tempNode.left) helperQueue.push(tempNode.left);
if (tempNode.right) helperQueue.push(tempNode.right);
}
}
return resCount;
};
```
> 利用完全二叉树性质
```typescript
function countNodes(root: TreeNode | null): number {
if (root === null) return 0;
let left: number = 0,
right: number = 0;
let curNode: TreeNode | null= root;
while (curNode !== null) {
left++;
curNode = curNode.left;
}
curNode = root;
while (curNode !== null) {
right++;
curNode = curNode.right;
}
if (left === right) {
return 2 ** left - 1;
}
return 1 + countNodes(root.left) + countNodes(root.right);
};
```
## C: ## C:
递归法 递归法
```c ```c
int countNodes(struct TreeNode* root) { int countNodes(struct TreeNode* root) {
@ -538,7 +594,7 @@ func _countNodes(_ root: TreeNode?) -> Int {
return 1 + leftCount + rightCount return 1 + leftCount + rightCount
} }
``` ```
> 层序遍历 > 层序遍历
```Swift ```Swift
func countNodes(_ root: TreeNode?) -> Int { func countNodes(_ root: TreeNode?) -> Int {
@ -564,7 +620,7 @@ func countNodes(_ root: TreeNode?) -> Int {
return res return res
} }
``` ```
> 利用完全二叉树性质 > 利用完全二叉树性质
```Swift ```Swift
func countNodes(_ root: TreeNode?) -> Int { func countNodes(_ root: TreeNode?) -> Int {

View File

@ -563,7 +563,135 @@ var invertTree = function(root) {
}; };
``` ```
### TypeScript
递归法:
```typescript
// 递归法(前序遍历)
function invertTree(root: TreeNode | null): TreeNode | null {
if (root === null) return root;
let tempNode: TreeNode | null = root.left;
root.left = root.right;
root.right = tempNode;
invertTree(root.left);
invertTree(root.right);
return root;
};
// 递归法(后序遍历)
function invertTree(root: TreeNode | null): TreeNode | null {
if (root === null) return root;
invertTree(root.left);
invertTree(root.right);
let tempNode: TreeNode | null = root.left;
root.left = root.right;
root.right = tempNode;
return root;
};
// 递归法(中序遍历)
function invertTree(root: TreeNode | null): TreeNode | null {
if (root === null) return root;
invertTree(root.left);
let tempNode: TreeNode | null = root.left;
root.left = root.right;
root.right = tempNode;
// 因为左右节点已经进行交换此时的root.left 是原先的root.right
invertTree(root.left);
return root;
};
```
迭代法:
```typescript
// 迭代法(栈模拟前序遍历)
function invertTree(root: TreeNode | null): TreeNode | null {
let helperStack: TreeNode[] = [];
let curNode: TreeNode,
tempNode: TreeNode | null;
if (root !== null) helperStack.push(root);
while (helperStack.length > 0) {
curNode = helperStack.pop()!;
// 入栈操作最好在交换节点之前进行,便于理解
if (curNode.right) helperStack.push(curNode.right);
if (curNode.left) helperStack.push(curNode.left);
tempNode = curNode.left;
curNode.left = curNode.right;
curNode.right = tempNode;
}
return root;
};
// 迭代法(栈模拟中序遍历-统一写法形式)
function invertTree(root: TreeNode | null): TreeNode | null {
let helperStack: (TreeNode | null)[] = [];
let curNode: TreeNode | null,
tempNode: TreeNode | null;
if (root !== null) helperStack.push(root);
while (helperStack.length > 0) {
curNode = helperStack.pop();
if (curNode !== null) {
if (curNode.right !== null) helperStack.push(curNode.right);
helperStack.push(curNode);
helperStack.push(null);
if (curNode.left !== null) helperStack.push(curNode.left);
} else {
curNode = helperStack.pop()!;
tempNode = curNode.left;
curNode.left = curNode.right;
curNode.right = tempNode;
}
}
return root;
};
// 迭代法(栈模拟后序遍历-统一写法形式)
function invertTree(root: TreeNode | null): TreeNode | null {
let helperStack: (TreeNode | null)[] = [];
let curNode: TreeNode | null,
tempNode: TreeNode | null;
if (root !== null) helperStack.push(root);
while (helperStack.length > 0) {
curNode = helperStack.pop();
if (curNode !== null) {
helperStack.push(curNode);
helperStack.push(null);
if (curNode.right !== null) helperStack.push(curNode.right);
if (curNode.left !== null) helperStack.push(curNode.left);
} else {
curNode = helperStack.pop()!;
tempNode = curNode.left;
curNode.left = curNode.right;
curNode.right = tempNode;
}
}
return root;
};
// 迭代法(队列模拟层序遍历)
function invertTree(root: TreeNode | null): TreeNode | null {
const helperQueue: TreeNode[] = [];
let curNode: TreeNode,
tempNode: TreeNode | null;
if (root !== null) helperQueue.push(root);
while (helperQueue.length > 0) {
for (let i = 0, length = helperQueue.length; i < length; i++) {
curNode = helperQueue.shift()!;
tempNode = curNode.left;
curNode.left = curNode.right;
curNode.right = tempNode;
if (curNode.left !== null) helperQueue.push(curNode.left);
if (curNode.right !== null) helperQueue.push(curNode.right);
}
}
return root;
};
```
### C: ### C:
递归法 递归法
```c ```c
struct TreeNode* invertTree(struct TreeNode* root){ struct TreeNode* invertTree(struct TreeNode* root){

View File

@ -348,7 +348,44 @@ MyQueue.prototype.empty = function() {
}; };
``` ```
TypeScript:
```typescript
class MyQueue {
private stackIn: number[]
private stackOut: number[]
constructor() {
this.stackIn = [];
this.stackOut = [];
}
push(x: number): void {
this.stackIn.push(x);
}
pop(): number {
if (this.stackOut.length === 0) {
while (this.stackIn.length > 0) {
this.stackOut.push(this.stackIn.pop()!);
}
}
return this.stackOut.pop()!;
}
peek(): number {
let temp: number = this.pop();
this.stackOut.push(temp);
return temp;
}
empty(): boolean {
return this.stackIn.length === 0 && this.stackOut.length === 0;
}
}
```
Swift Swift
```swift ```swift
class MyQueue { class MyQueue {

View File

@ -395,30 +395,102 @@ func maxSlidingWindow(nums []int, k int) []int {
Javascript: Javascript:
```javascript ```javascript
/**
* @param {number[]} nums
* @param {number} k
* @return {number[]}
*/
var maxSlidingWindow = function (nums, k) { var maxSlidingWindow = function (nums, k) {
// 队列数组(存放的是元素下标,为了取值方便) class MonoQueue {
const q = []; queue;
// 结果数组 constructor() {
const ans = []; this.queue = [];
for (let i = 0; i < nums.length; i++) { }
// 若队列不为空,且当前元素大于等于队尾所存下标的元素,则弹出队尾 enqueue(value) {
while (q.length && nums[i] >= nums[q[q.length - 1]]) { let back = this.queue[this.queue.length - 1];
q.pop(); while (back !== undefined && back < value) {
this.queue.pop();
back = this.queue[this.queue.length - 1];
}
this.queue.push(value);
}
dequeue(value) {
let front = this.front();
if (front === value) {
this.queue.shift();
}
}
front() {
return this.queue[0];
}
} }
// 入队当前元素下标 let helperQueue = new MonoQueue();
q.push(i); let i = 0, j = 0;
// 判断当前最大值(即队首元素)是否在窗口中,若不在便将其出队 let resArr = [];
if (q[0] <= i - k) { while (j < k) {
q.shift(); helperQueue.enqueue(nums[j++]);
} }
// 当达到窗口大小时便开始向结果中添加数据 resArr.push(helperQueue.front());
if (i >= k - 1) ans.push(nums[q[0]]); while (j < nums.length) {
} helperQueue.enqueue(nums[j]);
return ans; helperQueue.dequeue(nums[i]);
resArr.push(helperQueue.front());
i++, j++;
}
return resArr;
};
```
TypeScript
```typescript
function maxSlidingWindow(nums: number[], k: number): number[] {
/** 单调递减队列 */
class MonoQueue {
private queue: number[];
constructor() {
this.queue = [];
};
/** 入队value如果大于队尾元素则将队尾元素删除直至队尾元素大于value或者队列为空 */
public enqueue(value: number): void {
let back: number | undefined = this.queue[this.queue.length - 1];
while (back !== undefined && back < value) {
this.queue.pop();
back = this.queue[this.queue.length - 1];
}
this.queue.push(value);
};
/** 出队只有当队头元素等于value才出队 */
public dequeue(value: number): void {
let top: number | undefined = this.top();
if (top !== undefined && top === value) {
this.queue.shift();
}
}
public top(): number | undefined {
return this.queue[0];
}
}
const helperQueue: MonoQueue = new MonoQueue();
let i: number = 0,
j: number = 0;
let resArr: number[] = [];
while (j < k) {
helperQueue.enqueue(nums[j++]);
}
resArr.push(helperQueue.top()!);
while (j < nums.length) {
helperQueue.enqueue(nums[j]);
helperQueue.dequeue(nums[i]);
resArr.push(helperQueue.top()!);
j++, i++;
}
return resArr;
}; };
``` ```
Swift: Swift:
```Swift ```Swift
/// 双向链表 /// 双向链表
class DoublyListNode { class DoublyListNode {

View File

@ -4,23 +4,22 @@
</a> </a>
<p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>,贡献其他语言版本的代码,拥抱开源,让更多学习算法的小伙伴们收益!</strong></p> <p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>,贡献其他语言版本的代码,拥抱开源,让更多学习算法的小伙伴们收益!</strong></p>
## 343. 整数拆分 # 343. 整数拆分
[力扣题目链接](https://leetcode-cn.com/problems/integer-break/) [力扣题目链接](https://leetcode-cn.com/problems/integer-break/)
给定一个正整数 n将其拆分为至少两个正整数的和并使这些整数的乘积最大化。 返回你可以获得的最大乘积。 给定一个正整数 n将其拆分为至少两个正整数的和并使这些整数的乘积最大化。 返回你可以获得的最大乘积。
示例 1: 示例 1:
输入: 2 * 输入: 2
输出: 1 * 输出: 1
* 解释: 2 = 1 + 1, 1 × 1 = 1。
\解释: 2 = 1 + 1, 1 × 1 = 1。
示例 2: 示例 2:
输入: 10 * 输入: 10
输出: 36 * 输出: 36
解释: 10 = 3 + 3 + 4, 3 × 3 × 4 = 36。 * 解释: 10 = 3 + 3 + 4, 3 × 3 × 4 = 36。
说明: 你可以假设 n 不小于 2 且不大于 58。 * 说明: 你可以假设 n 不小于 2 且不大于 58。
## 思路 ## 思路
@ -193,7 +192,7 @@ public:
## 其他语言版本 ## 其他语言版本
Java ### Java
```Java ```Java
class Solution { class Solution {
public int integerBreak(int n) { public int integerBreak(int n) {
@ -212,7 +211,7 @@ class Solution {
} }
``` ```
Python ### Python
```python ```python
class Solution: class Solution:
def integerBreak(self, n: int) -> int: def integerBreak(self, n: int) -> int:
@ -226,7 +225,8 @@ class Solution:
dp[i] = max(dp[i], max(j * (i - j), j * dp[i - j])) dp[i] = max(dp[i], max(j * (i - j), j * dp[i - j]))
return dp[n] return dp[n]
``` ```
Go
### Go
```golang ```golang
func integerBreak(n int) int { func integerBreak(n int) int {
/** /**
@ -256,7 +256,7 @@ func max(a,b int) int{
} }
``` ```
Javascript: ### Javascript
```Javascript ```Javascript
var integerBreak = function(n) { var integerBreak = function(n) {
let dp = new Array(n + 1).fill(0) let dp = new Array(n + 1).fill(0)

View File

@ -358,6 +358,22 @@ PriorityQueue.prototype.compare = function(index1, index2) {
} }
``` ```
TypeScript
```typescript
function topKFrequent(nums: number[], k: number): number[] {
const countMap: Map<number, number> = new Map();
for (let num of nums) {
countMap.set(num, (countMap.get(num) || 0) + 1);
}
// tS没有最小堆的数据结构所以直接对整个数组进行排序取前k个元素
return [...countMap.entries()]
.sort((a, b) => b[1] - a[1])
.slice(0, k)
.map(i => i[0]);
};
```
----------------------- -----------------------

View File

@ -174,7 +174,7 @@ public:
```Java ```Java
class Solution { class Solution {
public int wiggleMaxLength(int[] nums) { public int wiggleMaxLength(int[] nums) {
if (nums == null || nums.length <= 1) { if (nums.length <= 1) {
return nums.length; return nums.length;
} }
//当前差值 //当前差值

View File

@ -210,6 +210,45 @@ class Solution {
} }
``` ```
二维数组版本(易于理解):
```Java
class Solution {
public boolean canPartition(int[] nums) {
int sum = 0;
for (int i = 0; i < nums.length; i++) {
sum += nums[i];
}
if (sum % 2 == 1)
return false;
int target = sum / 2;
//dp[i][j]代表可装物品为0-i背包容量为j的情况下背包内容量的最大价值
int[][] dp = new int[nums.length][target + 1];
//初始化,dp[0][j]的最大价值nums[0](if j > weight[i])
//dp[i][0]均为0不用初始化
for (int j = nums[0]; j <= target; j++) {
dp[0][j] = nums[0];
}
//遍历物品,遍历背包
//递推公式:
for (int i = 1; i < nums.length; i++) {
for (int j = 0; j <= target; j++) {
//背包容量可以容纳nums[i]
if (j >= nums[i]) {
dp[i][j] = Math.max(dp[i - 1][j], dp[i - 1][j - nums[i]] + nums[i]);
} else {
dp[i][j] = dp[i - 1][j];
}
}
}
return dp[nums.length - 1][target] == target;
}
}
```
Python Python
```python ```python
class Solution: class Solution:

View File

@ -183,28 +183,22 @@ public:
```java ```java
class Solution { class Solution {
public int eraseOverlapIntervals(int[][] intervals) { public int eraseOverlapIntervals(int[][] intervals) {
if (intervals.length < 2) return 0; Arrays.sort(intervals, (a, b) -> {
if (a[0] == a[0]) return a[1] - b[1];
Arrays.sort(intervals, new Comparator<int[]>() { return a[0] - b[0];
@Override
public int compare(int[] o1, int[] o2) {
if (o1[1] != o2[1]) {
return Integer.compare(o1[1],o2[1]);
} else {
return Integer.compare(o1[0],o2[0]);
}
}
}); });
int count = 1; int count = 0;
int edge = intervals[0][1]; int edge = Integer.MIN_VALUE;
for (int i = 1; i < intervals.length; i++) { for (int i = 0; i < intervals.length; i++) {
if (edge <= intervals[i][0]){ if (edge <= intervals[i][0]) {
count ++; //non overlap + 1
edge = intervals[i][1]; edge = intervals[i][1];
} else {
count++;
} }
} }
return intervals.length - count;
return count;
} }
} }
``` ```

View File

@ -272,7 +272,8 @@ Python
class Solution: class Solution:
def findTargetSumWays(self, nums: List[int], target: int) -> int: def findTargetSumWays(self, nums: List[int], target: int) -> int:
sumValue = sum(nums) sumValue = sum(nums)
if target > sumValue or (sumValue + target) % 2 == 1: return 0 #注意边界条件为 target>sumValue or target<-sumValue or (sumValue + target) % 2 == 1
if abs(target) > sumValue or (sumValue + target) % 2 == 1: return 0
bagSize = (sumValue + target) // 2 bagSize = (sumValue + target) // 2
dp = [0] * (bagSize + 1) dp = [0] * (bagSize + 1)
dp[0] = 1 dp[0] = 1

View File

@ -267,8 +267,32 @@ var removeDuplicates = function(s) {
}; };
``` ```
TypeScript
```typescript
function removeDuplicates(s: string): string {
const helperStack: string[] = [];
let i: number = 0;
while (i < s.length) {
let top: string = helperStack[helperStack.length - 1];
if (top === s[i]) {
helperStack.pop();
} else {
helperStack.push(s[i]);
}
i++;
}
let res: string = '';
while (helperStack.length > 0) {
res = helperStack.pop() + res;
}
return res;
};
```
C: C:
方法一:使用栈 方法一:使用栈
```c ```c
char * removeDuplicates(char * s){ char * removeDuplicates(char * s){
//求出字符串长度 //求出字符串长度

View File

@ -153,6 +153,8 @@ public:
Java Java
一维数组版本
```Java ```Java
class Solution { class Solution {
public int lastStoneWeightII(int[] stones) { public int lastStoneWeightII(int[] stones) {
@ -173,6 +175,41 @@ class Solution {
return sum - 2 * dp[target]; return sum - 2 * dp[target];
} }
} }
```
二维数组版本(便于理解)
```Java
class Solution {
public int lastStoneWeightII(int[] stones) {
int sum = 0;
for (int s : stones) {
sum += s;
}
int target = sum / 2;
//初始化dp[i][j]为可以放0-i物品背包容量为j的情况下背包中的最大价值
int[][] dp = new int[stones.length][target + 1];
//dp[i][0]默认初始化为0
//dp[0][j]取决于stones[0]
for (int j = stones[0]; j <= target; j++) {
dp[0][j] = stones[0];
}
for (int i = 1; i < stones.length; i++) {
for (int j = 1; j <= target; j++) {//注意是等于
if (j >= stones[i]) {
//不放:dp[i - 1][j] 放:dp[i - 1][j - stones[i]] + stones[i]
dp[i][j] = Math.max(dp[i - 1][j], dp[i - 1][j - stones[i]] + stones[i]);
} else {
dp[i][j] = dp[i - 1][j];
}
}
}
System.out.println(dp[stones.length - 1][target]);
return (sum - dp[stones.length - 1][target]) - dp[stones.length - 1][target];
}
}
``` ```
Python Python

View File

@ -227,7 +227,23 @@ function TreeNode(val, left, right) {
} }
``` ```
TypeScript
```typescript
class TreeNode {
public val: number;
public left: TreeNode | null;
public right: TreeNode | null;
constructor(val?: number, left?: TreeNode, right?: TreeNode) {
this.val = val === undefined ? 0 : val;
this.left = left === undefined ? null : left;
this.right = right === undefined ? null : right;
}
}
```
Swift: Swift:
```Swift ```Swift
class TreeNode<T> { class TreeNode<T> {
var value: T var value: T

View File

@ -522,7 +522,75 @@ var postorderTraversal = function(root, res = []) {
``` ```
TypeScript
```typescript
// 前序遍历(迭代法)
function preorderTraversal(root: TreeNode | null): number[] {
let helperStack: (TreeNode | null)[] = [];
let res: number[] = [];
let curNode: TreeNode | null;
if (root === null) return res;
helperStack.push(root);
while (helperStack.length > 0) {
curNode = helperStack.pop()!;
if (curNode !== null) {
if (curNode.right !== null) helperStack.push(curNode.right);
helperStack.push(curNode);
helperStack.push(null);
if (curNode.left !== null) helperStack.push(curNode.left);
} else {
curNode = helperStack.pop()!;
res.push(curNode.val);
}
}
return res;
};
// 中序遍历(迭代法)
function inorderTraversal(root: TreeNode | null): number[] {
let helperStack: (TreeNode | null)[] = [];
let res: number[] = [];
let curNode: TreeNode | null;
if (root === null) return res;
helperStack.push(root);
while (helperStack.length > 0) {
curNode = helperStack.pop()!;
if (curNode !== null) {
if (curNode.right !== null) helperStack.push(curNode.right);
helperStack.push(curNode);
helperStack.push(null);
if (curNode.left !== null) helperStack.push(curNode.left);
} else {
curNode = helperStack.pop()!;
res.push(curNode.val);
}
}
return res;
};
// 后序遍历(迭代法)
function postorderTraversal(root: TreeNode | null): number[] {
let helperStack: (TreeNode | null)[] = [];
let res: number[] = [];
let curNode: TreeNode | null;
if (root === null) return res;
helperStack.push(root);
while (helperStack.length > 0) {
curNode = helperStack.pop()!;
if (curNode !== null) {
if (curNode.right !== null) helperStack.push(curNode.right);
helperStack.push(curNode);
helperStack.push(null);
if (curNode.left !== null) helperStack.push(curNode.left);
} else {
curNode = helperStack.pop()!;
res.push(curNode.val);
}
}
return res;
};
```
----------------------- -----------------------
<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div> <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

View File

@ -454,6 +454,61 @@ var postorderTraversal = function(root, res = []) {
}; };
``` ```
TypeScript:
```typescript
// 前序遍历(迭代法)
function preorderTraversal(root: TreeNode | null): number[] {
if (root === null) return [];
let res: number[] = [];
let helperStack: TreeNode[] = [];
let curNode: TreeNode = root;
helperStack.push(curNode);
while (helperStack.length > 0) {
curNode = helperStack.pop()!;
res.push(curNode.val);
if (curNode.right !== null) helperStack.push(curNode.right);
if (curNode.left !== null) helperStack.push(curNode.left);
}
return res;
};
// 中序遍历(迭代法)
function inorderTraversal(root: TreeNode | null): number[] {
let helperStack: TreeNode[] = [];
let res: number[] = [];
if (root === null) return res;
let curNode: TreeNode | null = root;
while (curNode !== null || helperStack.length > 0) {
if (curNode !== null) {
helperStack.push(curNode);
curNode = curNode.left;
} else {
curNode = helperStack.pop()!;
res.push(curNode.val);
curNode = curNode.right;
}
}
return res;
};
// 后序遍历(迭代法)
function postorderTraversal(root: TreeNode | null): number[] {
let helperStack: TreeNode[] = [];
let res: number[] = [];
let curNode: TreeNode;
if (root === null) return res;
helperStack.push(root);
while (helperStack.length > 0) {
curNode = helperStack.pop()!;
res.push(curNode.val);
if (curNode.left !== null) helperStack.push(curNode.left);
if (curNode.right !== null) helperStack.push(curNode.right);
}
return res.reverse();
};
```
Swift: Swift:
> 迭代法前序遍历 > 迭代法前序遍历

View File

@ -270,40 +270,6 @@ func postorderTraversal(root *TreeNode) (res []int) {
} }
``` ```
javaScript:
```js
前序遍历:
var preorderTraversal = function(root, res = []) {
if (!root) return res;
res.push(root.val);
preorderTraversal(root.left, res)
preorderTraversal(root.right, res)
return res;
};
中序遍历:
var inorderTraversal = function(root, res = []) {
if (!root) return res;
inorderTraversal(root.left, res);
res.push(root.val);
inorderTraversal(root.right, res);
return res;
};
后序遍历:
var postorderTraversal = function(root, res = []) {
if (!root) return res;
postorderTraversal(root.left, res);
postorderTraversal(root.right, res);
res.push(root.val);
return res;
};
```
Javascript版本 Javascript版本
前序遍历: 前序遍历:
@ -358,7 +324,51 @@ var postorderTraversal = function(root) {
}; };
``` ```
TypeScript:
```typescript
// 前序遍历
function preorderTraversal(node: TreeNode | null): number[] {
function traverse(node: TreeNode | null, res: number[]): void {
if (node === null) return;
res.push(node.val);
traverse(node.left, res);
traverse(node.right, res);
}
const res: number[] = [];
traverse(node, res);
return res;
}
// 中序遍历
function inorderTraversal(node: TreeNode | null): number[] {
function traverse(node: TreeNode | null, res: number[]): void {
if (node === null) return;
traverse(node.left, res);
res.push(node.val);
traverse(node.right, res);
}
const res: number[] = [];
traverse(node, res);
return res;
}
// 后序遍历
function postorderTraversal(node: TreeNode | null): number[] {
function traverse(node: TreeNode | null, res: number[]): void {
if (node === null) return;
traverse(node.left, res);
traverse(node.right, res);
res.push(node.val);
}
const res: number[] = [];
traverse(node, res);
return res;
}
```
C: C:
```c ```c
//前序遍历: //前序遍历:
void preOrderTraversal(struct TreeNode* root, int* ret, int* returnSize) { void preOrderTraversal(struct TreeNode* root, int* ret, int* returnSize) {

View File

@ -135,7 +135,6 @@ Markdown支持部分html例如这样
----------------------- -----------------------
* 作者微信:[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) * 作者微信:[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
* B站视频[代码随想录](https://space.bilibili.com/525438321) * B站视频[代码随想录](https://space.bilibili.com/525438321)

View File

@ -3,11 +3,12 @@
<img src="https://code-thinking-1253855093.file.myqcloud.com/pics/20210924105952.png" width="1000"/> <img src="https://code-thinking-1253855093.file.myqcloud.com/pics/20210924105952.png" width="1000"/>
</a> </a>
<p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>,贡献其他语言版本的代码,拥抱开源,让更多学习算法的小伙伴们收益!</strong></p> <p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>,贡献其他语言版本的代码,拥抱开源,让更多学习算法的小伙伴们收益!</strong></p>
# 动态规划关于01背包问题你该了解这些 # 动态规划关于01背包问题你该了解这些
这周我们正式开始讲解背包问题! 这周我们正式开始讲解背包问题!
背包问题的经典资料当然是:背包九讲。在公众号「代码随想录」后台回复:背包九讲,就可以获得背包九讲的PDF 背包问题的经典资料当然是:背包九讲。在公众号「代码随想录」后台回复:背包九讲,就可以获得背包九讲的pdf
但说实话,背包九讲对于小白来说确实不太友好,看起来还是有点费劲的,而且都是伪代码理解起来也吃力。 但说实话,背包九讲对于小白来说确实不太友好,看起来还是有点费劲的,而且都是伪代码理解起来也吃力。
@ -32,7 +33,7 @@ leetcode上没有纯01背包的问题都是01背包应用方面的题目
## 01 背包 ## 01 背包
N件物品和一个最多能背重量为W 的背包。第i件物品的重量是weight[i]得到的价值是value[i] 。**每件物品只能用一次**,求解将哪些物品装入背包里物品价值总和最大。 n件物品和一个最多能背重量为w 的背包。第i件物品的重量是weight[i]得到的价值是value[i] 。**每件物品只能用一次**,求解将哪些物品装入背包里物品价值总和最大。
![动态规划-背包问题](https://img-blog.csdnimg.cn/20210117175428387.jpg) ![动态规划-背包问题](https://img-blog.csdnimg.cn/20210117175428387.jpg)
@ -40,7 +41,7 @@ leetcode上没有纯01背包的问题都是01背包应用方面的题目
这样其实是没有从底向上去思考,而是习惯性想到了背包,那么暴力的解法应该是怎么样的呢? 这样其实是没有从底向上去思考,而是习惯性想到了背包,那么暴力的解法应该是怎么样的呢?
每一件物品其实只有两个状态,取或者不取,所以可以使用回溯法搜索出所有的情况,那么时间复杂度就是$O(2^n)$这里的n表示物品数量。 每一件物品其实只有两个状态,取或者不取,所以可以使用回溯法搜索出所有的情况,那么时间复杂度就是$o(2^n)$这里的n表示物品数量。
**所以暴力的解法是指数级别的时间复杂度。进而才需要动态规划的解法来进行优化!** **所以暴力的解法是指数级别的时间复杂度。进而才需要动态规划的解法来进行优化!**
@ -109,7 +110,7 @@ for (int j = 0 ; j < weight[0]; j++) { // 当然这一步如果把dp数组
dp[0][j] = 0; dp[0][j] = 0;
} }
// 正序遍历 // 正序遍历
for (int j = weight[0]; j <= bagWeight; j++) { for (int j = weight[0]; j <= bagweight; j++) {
dp[0][j] = value[0]; dp[0][j] = value[0];
} }
``` ```
@ -135,8 +136,8 @@ dp[0][j] 和 dp[i][0] 都已经初始化了,那么其他下标应该初始化
``` ```
// 初始化 dp // 初始化 dp
vector<vector<int>> dp(weight.size(), vector<int>(bagWeight + 1, 0)); vector<vector<int>> dp(weight.size(), vector<int>(bagweight + 1, 0));
for (int j = weight[0]; j <= bagWeight; j++) { for (int j = weight[0]; j <= bagweight; j++) {
dp[0][j] = value[0]; dp[0][j] = value[0];
} }
@ -160,7 +161,7 @@ for (int j = weight[0]; j <= bagWeight; j++) {
``` ```
// weight数组的大小 就是物品个数 // weight数组的大小 就是物品个数
for(int i = 1; i < weight.size(); i++) { // 遍历物品 for(int i = 1; i < weight.size(); i++) { // 遍历物品
for(int j = 0; j <= bagWeight; j++) { // 遍历背包容量 for(int j = 0; j <= bagweight; j++) { // 遍历背包容量
if (j < weight[i]) dp[i][j] = dp[i - 1][j]; if (j < weight[i]) dp[i][j] = dp[i - 1][j];
else dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - weight[i]] + value[i]); else dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - weight[i]] + value[i]);
@ -174,7 +175,7 @@ for(int i = 1; i < weight.size(); i++) { // 遍历物品
``` ```
// weight数组的大小 就是物品个数 // weight数组的大小 就是物品个数
for(int j = 0; j <= bagWeight; j++) { // 遍历背包容量 for(int j = 0; j <= bagweight; j++) { // 遍历背包容量
for(int i = 1; i < weight.size(); i++) { // 遍历物品 for(int i = 1; i < weight.size(); i++) { // 遍历物品
if (j < weight[i]) dp[i][j] = dp[i - 1][j]; if (j < weight[i]) dp[i][j] = dp[i - 1][j];
else dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - weight[i]] + value[i]); else dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - weight[i]] + value[i]);
@ -219,32 +220,32 @@ dp[i-1][j]和dp[i - 1][j - weight[i]] 都在dp[i][j]的左上角方向(包括
主要就是自己没有动手推导一下dp数组的演变过程如果推导明白了代码写出来就算有问题只要把dp数组打印出来对比一下和自己推导的有什么差异很快就可以发现问题了。 主要就是自己没有动手推导一下dp数组的演变过程如果推导明白了代码写出来就算有问题只要把dp数组打印出来对比一下和自己推导的有什么差异很快就可以发现问题了。
## 完整C++测试代码 ## 完整c++测试代码
```CPP ```cpp
void test_2_wei_bag_problem1() { void test_2_wei_bag_problem1() {
vector<int> weight = {1, 3, 4}; vector<int> weight = {1, 3, 4};
vector<int> value = {15, 20, 30}; vector<int> value = {15, 20, 30};
int bagWeight = 4; int bagweight = 4;
// 二维数组 // 二维数组
vector<vector<int>> dp(weight.size(), vector<int>(bagWeight + 1, 0)); vector<vector<int>> dp(weight.size(), vector<int>(bagweight + 1, 0));
// 初始化 // 初始化
for (int j = weight[0]; j <= bagWeight; j++) { for (int j = weight[0]; j <= bagweight; j++) {
dp[0][j] = value[0]; dp[0][j] = value[0];
} }
// weight数组的大小 就是物品个数 // weight数组的大小 就是物品个数
for(int i = 1; i < weight.size(); i++) { // 遍历物品 for(int i = 1; i < weight.size(); i++) { // 遍历物品
for(int j = 0; j <= bagWeight; j++) { // 遍历背包容量 for(int j = 0; j <= bagweight; j++) { // 遍历背包容量
if (j < weight[i]) dp[i][j] = dp[i - 1][j]; if (j < weight[i]) dp[i][j] = dp[i - 1][j];
else dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - weight[i]] + value[i]); else dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - weight[i]] + value[i]);
} }
} }
cout << dp[weight.size() - 1][bagWeight] << endl; cout << dp[weight.size() - 1][bagweight] << endl;
} }
int main() { int main() {
@ -267,48 +268,45 @@ int main() {
## 其他语言版本 ## 其他语言版本
Java ### java
```java ```java
public static void main(String[] args) { public static void main(string[] args) {
int[] weight = {1, 3, 4}; int[] weight = {1, 3, 4};
int[] value = {15, 20, 30}; int[] value = {15, 20, 30};
int bagSize = 4; int bagsize = 4;
testWeightBagProblem(weight, value, bagSize); testweightbagproblem(weight, value, bagsize);
} }
public static void testWeightBagProblem(int[] weight, int[] value, int bagSize){ public static void testweightbagproblem(int[] weight, int[] value, int bagsize){
int wLen = weight.length, value0 = 0; int wlen = weight.length, value0 = 0;
//定义dp数组dp[i][j]表示背包容量为j时前i个物品能获得的最大价值 //定义dp数组dp[i][j]表示背包容量为j时前i个物品能获得的最大价值
int[][] dp = new int[wLen + 1][bagSize + 1]; int[][] dp = new int[wlen + 1][bagsize + 1];
//初始化背包容量为0时能获得的价值都为0 //初始化背包容量为0时能获得的价值都为0
for (int i = 0; i <= wLen; i++){ for (int i = 0; i <= wlen; i++){
dp[i][0] = value0; dp[i][0] = value0;
} }
//遍历顺序:先遍历物品,再遍历背包容量 //遍历顺序:先遍历物品,再遍历背包容量
for (int i = 1; i <= wLen; i++){ for (int i = 1; i <= wlen; i++){
for (int j = 1; j <= bagSize; j++){ for (int j = 1; j <= bagsize; j++){
if (j < weight[i - 1]){ if (j < weight[i - 1]){
dp[i][j] = dp[i - 1][j]; dp[i][j] = dp[i - 1][j];
}else{ }else{
dp[i][j] = Math.max(dp[i - 1][j], dp[i - 1][j - weight[i - 1]] + value[i - 1]); dp[i][j] = math.max(dp[i - 1][j], dp[i - 1][j - weight[i - 1]] + value[i - 1]);
} }
} }
} }
//打印dp数组 //打印dp数组
for (int i = 0; i <= wLen; i++){ for (int i = 0; i <= wlen; i++){
for (int j = 0; j <= bagSize; j++){ for (int j = 0; j <= bagsize; j++){
System.out.print(dp[i][j] + " "); system.out.print(dp[i][j] + " ");
} }
System.out.print("\n"); system.out.print("\n");
} }
} }
``` ```
### python
Python
```python ```python
def test_2_wei_bag_problem1(bag_size, weight, value) -> int: def test_2_wei_bag_problem1(bag_size, weight, value) -> int:
rows, cols = len(weight), bag_size + 1 rows, cols = len(weight), bag_size + 1
@ -343,26 +341,26 @@ if __name__ == "__main__":
``` ```
Go ### go
```go ```go
func test_2_wei_bag_problem1(weight, value []int, bagWeight int) int { func test_2_wei_bag_problem1(weight, value []int, bagweight int) int {
// 定义dp数组 // 定义dp数组
dp := make([][]int, len(weight)) dp := make([][]int, len(weight))
for i, _ := range dp { for i, _ := range dp {
dp[i] = make([]int, bagWeight+1) dp[i] = make([]int, bagweight+1)
} }
// 初始化 // 初始化
for j := bagWeight; j >= weight[0]; j-- { for j := bagweight; j >= weight[0]; j-- {
dp[0][j] = dp[0][j-weight[0]] + value[0] dp[0][j] = dp[0][j-weight[0]] + value[0]
} }
// 递推公式 // 递推公式
for i := 1; i < len(weight); i++ { for i := 1; i < len(weight); i++ {
//正序,也可以倒序 //正序,也可以倒序
for j := weight[i];j<= bagWeight ; j++ { for j := weight[i];j<= bagweight ; j++ {
dp[i][j] = max(dp[i-1][j], dp[i-1][j-weight[i]]+value[i]) dp[i][j] = max(dp[i-1][j], dp[i-1][j-weight[i]]+value[i])
} }
} }
return dp[len(weight)-1][bagWeight] return dp[len(weight)-1][bagweight]
} }
func max(a,b int) int { func max(a,b int) int {
@ -379,19 +377,19 @@ func main() {
} }
``` ```
javaScript: ### javascript
```js ```js
function testWeightBagProblem (wight, value, size) { function testweightbagproblem (wight, value, size) {
const len = wight.length, const len = wight.length,
dp = Array.from({length: len + 1}).map( dp = array.from({length: len + 1}).map(
() => Array(size + 1).fill(0) () => array(size + 1).fill(0)
); );
for(let i = 1; i <= len; i++) { for(let i = 1; i <= len; i++) {
for(let j = 0; j <= size; j++) { for(let j = 0; j <= size; j++) {
if(wight[i - 1] <= j) { if(wight[i - 1] <= j) {
dp[i][j] = Math.max( dp[i][j] = math.max(
dp[i - 1][j], dp[i - 1][j],
value[i - 1] + dp[i - 1][j - wight[i - 1]] value[i - 1] + dp[i - 1][j - wight[i - 1]]
) )

View File

@ -210,7 +210,7 @@ int main() {
## 其他语言版本 ## 其他语言版本
Java ### Java
```java ```java
public static void main(String[] args) { public static void main(String[] args) {
@ -240,7 +240,7 @@ Java
Python ### Python
```python ```python
def test_1_wei_bag_problem(): def test_1_wei_bag_problem():
weight = [1, 3, 4] weight = [1, 3, 4]
@ -260,7 +260,7 @@ def test_1_wei_bag_problem():
test_1_wei_bag_problem() test_1_wei_bag_problem()
``` ```
Go ### Go
```go ```go
func test_1_wei_bag_problem(weight, value []int, bagWeight int) int { func test_1_wei_bag_problem(weight, value []int, bagWeight int) int {
// 定义 and 初始化 // 定义 and 初始化
@ -292,7 +292,7 @@ func main() {
} }
``` ```
javaScript: ### javaScript
```js ```js

View File

@ -183,11 +183,9 @@ private static void testCompletePack(){
int[] value = {15, 20, 30}; int[] value = {15, 20, 30};
int bagWeight = 4; int bagWeight = 4;
int[] dp = new int[bagWeight + 1]; int[] dp = new int[bagWeight + 1];
for (int i = 0; i < weight.length; i++){ for (int i = 0; i < weight.length; i++){ // 遍历物品
for (int j = 1; j <= bagWeight; j++){ for (int j = weight[i]; j <= bagWeight; j++){ // 遍历背包容量
if (j - weight[i] >= 0){ dp[j] = Math.max(dp[j], dp[j - weight[i]] + value[i]);
dp[j] = Math.max(dp[j], dp[j - weight[i]] + value[i]);
}
} }
} }
for (int maxValue : dp){ for (int maxValue : dp){
@ -201,8 +199,8 @@ private static void testCompletePackAnotherWay(){
int[] value = {15, 20, 30}; int[] value = {15, 20, 30};
int bagWeight = 4; int bagWeight = 4;
int[] dp = new int[bagWeight + 1]; int[] dp = new int[bagWeight + 1];
for (int i = 1; i <= bagWeight; i++){ for (int i = 1; i <= bagWeight; i++){ // 遍历背包容量
for (int j = 0; j < weight.length; j++){ for (int j = 0; j < weight.length; j++){ // 遍历物品
if (i - weight[j] >= 0){ if (i - weight[j] >= 0){
dp[i] = Math.max(dp[i], dp[i - weight[j]] + value[j]); dp[i] = Math.max(dp[i], dp[i - weight[j]] + value[j]);
} }