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Merge branch 'master' into patch-3

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Carl Sun
2021-05-14 09:41:59 +08:00
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parent cd919ae432 eabe8dbd36
commit 5034c340fb
55 changed files with 1582 additions and 89 deletions
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20
problems/0027.移除元素.md
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@ -123,6 +123,24 @@ public:
Java：
```java
class Solution {
public int removeElement(int[] nums, int val) {
// 快慢指针
int fastIndex = 0;
int slowIndex;
for (slowIndex = 0; fastIndex < nums.length; fastIndex++) {
if (nums[fastIndex] != val) {
nums[slowIndex] = nums[fastIndex];
slowIndex++;
}
}
return slowIndex;
}
}
```
Python：
@ -172,4 +190,4 @@ var removeElement = (nums, val) => {
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

30
problems/0056.合并区间.md
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@ -137,7 +137,35 @@ public:
Java：
```java
class Solution {
public int[][] merge(int[][] intervals) {
List<int[]> res = new LinkedList<>();
Arrays.sort(intervals, new Comparator<int[]>() {
@Override
public int compare(int[] o1, int[] o2) {
if (o1[0] != o2[0]) {
return Integer.compare(o1[0],o2[0]);
} else {
return Integer.compare(o1[1],o2[1]);
}
}
});
int start = intervals[0][0];
for (int i = 1; i < intervals.length; i++) {
if (intervals[i][0] > intervals[i - 1][1]) {
res.add(new int[]{start, intervals[i - 1][1]});
start = intervals[i][0];
} else {
intervals[i][1] = Math.max(intervals[i][1], intervals[i - 1][1]);
}
}
res.add(new int[]{start, intervals[intervals.length - 1][1]});
return res.toArray(new int[res.size()][]);
}
}
```
Python：
@ -151,4 +179,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

18
problems/0070.爬楼梯完全背包版本.md
View File

@ -127,7 +127,23 @@ public:
Java：
```java
class Solution {
public int climbStairs(int n) {
int[] dp = new int[n + 1];
int[] weight = {1,2};
dp[0] = 1;
for (int i = 0; i <= n; i++) {
for (int j = 0; j < weight.length; j++) {
if (i >= weight[j]) dp[i] += dp[i - weight[j]];
}
}
return dp[n];
}
}
```
Python：
@ -141,4 +157,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

15
problems/0098.验证二叉搜索树.md
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@ -254,6 +254,19 @@ public:
Java：
```java
class Solution {
public boolean isValidBST(TreeNode root) {
return isValidBST_2(root, Long.MIN_VALUE, Long.MAX_VALUE);
}
public boolean isValidBST_2 (TreeNode root, long lo, long hi) {
if (root == null) return true;
if (root.val >= hi || root.val <= lo) return false;
return isValidBST_2(root.left,lo,root.val) && isValidBST_2(root.right,root.val,hi);
}
}
```
Python：
@ -286,4 +299,4 @@ func isBST(root *TreeNode, min, max int) bool {
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

89
problems/0101.对称二叉树.md
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@ -254,7 +254,94 @@ public:
## 其他语言版本
Java：
```java
public class N0101 {
/**
* 解法1：DFS，递归。
*/
public boolean isSymmetric2(TreeNode root) {
if (root == null) {
return false;
}
return compare(root.left, root.right);
}
private boolean compare(TreeNode left, TreeNode right) {
if (left == null && right == null) {
return true;
}
if (left != null && right == null) {
return false;
}
if (left == null && right != null) {
return false;
}
if (left.val == right.val) {
return compare(left.left, right.right) && compare(left.right, right.left);
}
return false;
}
/**
* 解法2：DFS，迭代
*/
public boolean isSymmetric3(TreeNode root) {
if (root == null) {
return false;
}
if (!equal(root.left, root.right)) {
return false;
}
Deque<TreeNode> st = new LinkedList<>();
st.push(root.right);
st.push(root.left);
TreeNode curR = root.right;
TreeNode curL = root.left;
while (!st.isEmpty()) {
curL = st.pop();
curR = st.pop();
// 前序，处理
if (!equal(curL, curR)) {
return false;
}
if (curR != null && curL != null) {
st.push(curL.right);
st.push(curR.left);
st.push(curR.right);
st.push(curL.left);
}
}
return true;
}
private boolean equal(TreeNode l, TreeNode r) {
if (l == null && r == null) {
return true;
}
if (l != null && r == null) {
return false;
}
if (l == null && r != null) {
return false;
}
if (l.val == r.val) {
return true;
}
return false;
}
}
```
Python：
@ -283,4 +370,4 @@ const check = (leftPtr, rightPtr) => {
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

228
problems/0102.二叉树的层序遍历.md
View File

@ -420,54 +420,236 @@ public:
Java：
```Java
// 102.二叉树的层序遍历
class Solution {
public List<List<Integer>> resList=new ArrayList<List<Integer>>();
public List<List<Integer>> resList = new ArrayList<List<Integer>>();
public List<List<Integer>> levelOrder(TreeNode root) {
//checkFun01(root,0);
checkFun02(root);
return resList;
}
//DFS--递归方式
public void checkFun01(TreeNode node,Integer deep){
if(node==null) return;
//DFS--递归方式
public void checkFun01(TreeNode node, Integer deep) {
if (node == null) return;
deep++;
if(resList.size()<deep){
if (resList.size() < deep) {
//当层级增加时，list的Item也增加，利用list的索引值进行层级界定
List<Integer> item=new ArrayList<Integer>();
List<Integer> item = new ArrayList<Integer>();
resList.add(item);
}
resList.get(deep-1).add(node.val);
checkFun01(node.left,deep);
checkFun01(node.right,deep);
resList.get(deep - 1).add(node.val);
checkFun01(node.left, deep);
checkFun01(node.right, deep);
}
//BFS--迭代方式--借助队列
public void checkFun02(TreeNode node){
if(node==null) return;
Queue<TreeNode> que=new LinkedList<TreeNode>();
public void checkFun02(TreeNode node) {
if (node == null) return;
Queue<TreeNode> que = new LinkedList<TreeNode>();
que.offer(node);
while(!que.isEmpty()){
List<Integer> itemList=new ArrayList<Integer>();
int len=que.size();
while (!que.isEmpty()) {
List<Integer> itemList = new ArrayList<Integer>();
int len = que.size();
while(len>0){
TreeNode tmpNode=que.poll();
while (len > 0) {
TreeNode tmpNode = que.poll();
itemList.add(tmpNode.val);
if(tmpNode.left!=null) que.offer(tmpNode.left);
if(tmpNode.right!=null) que.offer(tmpNode.right);
if (tmpNode.left != null) que.offer(tmpNode.left);
if (tmpNode.right != null) que.offer(tmpNode.right);
len--;
}
resList.add(itemList);
}
}
}
// 107. 二叉树的层序遍历 II
public class N0107 {
/**
* 解法：队列，迭代。
* 层序遍历，再翻转数组即可。
*/
public List<List<Integer>> solution1(TreeNode root) {
List<List<Integer>> list = new ArrayList<>();
Deque<TreeNode> que = new LinkedList<>();
if (root == null) {
return list;
}
que.offerLast(root);
while (!que.isEmpty()) {
List<Integer> levelList = new ArrayList<>();
int levelSize = que.size();
for (int i = 0; i < levelSize; i++) {
TreeNode peek = que.peekFirst();
levelList.add(que.pollFirst().val);
if (peek.left != null) {
que.offerLast(peek.left);
}
if (peek.right != null) {
que.offerLast(peek.right);
}
}
list.add(levelList);
}
List<List<Integer>> result = new ArrayList<>();
for (int i = list.size() - 1; i >= 0; i-- ) {
result.add(list.get(i));
}
return result;
}
}
// 199.二叉树的右视图
public class N0199 {
/**
* 解法：队列，迭代。
* 每次返回每层的最后一个字段即可。
*
* 小优化：每层右孩子先入队。代码略。
*/
public List<Integer> rightSideView(TreeNode root) {
List<Integer> list = new ArrayList<>();
Deque<TreeNode> que = new LinkedList<>();
if (root == null) {
return list;
}
que.offerLast(root);
while (!que.isEmpty()) {
int levelSize = que.size();
for (int i = 0; i < levelSize; i++) {
TreeNode poll = que.pollFirst();
if (poll.left != null) {
que.addLast(poll.left);
}
if (poll.right != null) {
que.addLast(poll.right);
}
if (i == levelSize - 1) {
list.add(poll.val);
}
}
}
return list;
}
}
// 637. 二叉树的层平均值
public class N0637 {
/**
* 解法：队列，迭代。
* 每次返回每层的最后一个字段即可。
*/
public List<Double> averageOfLevels(TreeNode root) {
List<Double> list = new ArrayList<>();
Deque<TreeNode> que = new LinkedList<>();
if (root == null) {
return list;
}
que.offerLast(root);
while (!que.isEmpty()) {
TreeNode peek = que.peekFirst();
int levelSize = que.size();
double levelSum = 0.0;
for (int i = 0; i < levelSize; i++) {
TreeNode poll = que.pollFirst();
levelSum += poll.val;
if (poll.left != null) {
que.addLast(poll.left);
}
if (poll.right != null) {
que.addLast(poll.right);
}
}
list.add(levelSum / levelSize);
}
return list;
}
}
// 429. N 叉树的层序遍历
public class N0429 {
/**
* 解法1：队列，迭代。
*/
public List<List<Integer>> levelOrder(Node root) {
List<List<Integer>> list = new ArrayList<>();
Deque<Node> que = new LinkedList<>();
if (root == null) {
return list;
}
que.offerLast(root);
while (!que.isEmpty()) {
int levelSize = que.size();
List<Integer> levelList = new ArrayList<>();
for (int i = 0; i < levelSize; i++) {
Node poll = que.pollFirst();
levelList.add(poll.val);
List<Node> children = poll.children;
if (children == null || children.size() == 0) {
continue;
}
for (Node child : children) {
if (child != null) {
que.offerLast(child);
}
}
}
list.add(levelList);
}
return list;
}
class Node {
public int val;
public List<Node> children;
public Node() {}
public Node(int _val) {
val = _val;
}
public Node(int _val, List<Node> _children) {
val = _val;
children = _children;
}
}
}
```

22
problems/0104.二叉树的最大深度.md
View File

@ -231,6 +231,18 @@ public:
Java：
```java
class Solution {
public int maxDepth(TreeNode root) {
if (root == null) {
return 0;
}
int leftdeep = maxDepth(root.left);
int rightdeep = maxDepth(root.right);
return 1+Math.max(leftdeep,rightdeep);
}
}
```
Python：
@ -239,10 +251,16 @@ Python：
Go：
JavaScript
```javascript
var maxDepth = function(root) {
if (!root) return root
return 1 + Math.max(maxDepth(root.left), maxDepth(root.right))
};
```
-----------------------
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

43
problems/0106.从中序与后序遍历序列构造二叉树.md
View File

@ -582,6 +582,47 @@ tree2 的前序遍历是[1 2 3]， 后序遍历是[3 2 1]。
Java：
```java
class Solution {
public TreeNode buildTree(int[] inorder, int[] postorder) {
if (inorder.length == 0 || postorder.length == 0) return null;
return buildTree(inorder, postorder,0,inorder.length,0,postorder.length);
}
private TreeNode buildTree(int[] inorder, int[] postorder, int infrom, int into,
int postfrom, int postto) {
if (postfrom == postto) return null;
int rootValue = postorder[postto - 1];
TreeNode root = new TreeNode(rootValue);
if (postfrom + 1 == postto) return root;
int splitNum = postto - 1;
for (int i = infrom; i < into; i++) {
if (inorder[i] == rootValue) {
splitNum = i;
break;
}
}
int inLeftBegin = infrom;
int inLeftEnd = splitNum;
int inRightBegin = splitNum + 1;
int inRightEnd = into;
int postLeftBegin = postfrom;
int postLeftEnd = postLeftBegin + (splitNum - inLeftBegin);
int postRightBegin = postLeftBegin + (splitNum - inLeftBegin);
int postRightEnd = postto - 1;
root.left = buildTree(inorder,postorder,inLeftBegin,inLeftEnd,postLeftBegin,postLeftEnd);
root.right = buildTree(inorder,postorder,inRightBegin,inRightEnd,postRightBegin,postRightEnd);
return root;
}
}
```
Python：
@ -596,4 +637,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

22
problems/0108.将有序数组转换为二叉搜索树.md
View File

@ -209,6 +209,26 @@ public:
Java：
```java
class Solution {
public TreeNode sortedArrayToBST(int[] nums) {
return sortArr(nums,0,nums.length);
}
private TreeNode sortArr(int[] nums, int lo, int hi) {
if (lo == hi) return null;
int rootIdx = (lo + hi)/2;
int rootValue = nums[rootIdx];
TreeNode root = new TreeNode(rootValue);
root.left = sortArr(nums,lo,rootIdx);
root.right = sortArr(nums,rootIdx+1,hi);
return root;
}
}
```
Python：
@ -223,4 +243,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

23
problems/0110.平衡二叉树.md
View File

@ -354,6 +354,29 @@ public:
## 其他语言版本
Java：
```java
class Solution {
boolean flag = true;
public boolean isBalanced(TreeNode root) {
high(root);
return flag;
}
private int high (TreeNode root) {
if (root == null) return 0;
if (flag) {
int left = high(root.left);
int right = high(root.right);
if (Math.abs(left - right) > 1) flag = false;
return Math.max(left,right) + 1;
} else {
return -1;
}
}
}
```
Python：

14
problems/0111.二叉树的最小深度.md
View File

@ -194,6 +194,20 @@ public:
Java：
```java
class Solution {
public int minDepth(TreeNode root) {
if (root == null) return 0;
int leftDeep = minDepth(root.left);
int rightDeep = minDepth(root.right);
if (root.left == null && root.right != null) return 1+rightDeep;
if (root.left != null && root.right == null) return 1+leftDeep;
return Math.min(leftDeep,rightDeep)+1;
}
}
```
Python：

20
problems/0112.路径总和.md
View File

@ -305,6 +305,24 @@ public:
Java：
```java
class Solution {
private boolean flag = false;
public boolean hasPathSum(TreeNode root, int targetSum) {
has_2(root,targetSum);
return flag;
}
public void has_2 (TreeNode root, int count) {
if (root == null) return;
if (root.left == null && root.right == null && count == root.val) {
flag = true;
}
if (root.left != null) has_2(root.left,count - root.val);
if (root.right != null) has_2(root.right,count - root.val);
}
}
```
Python：
@ -387,4 +405,4 @@ let pathSum = function (root, targetSum) {
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

20
problems/0122.买卖股票的最佳时机II.md
View File

@ -135,7 +135,23 @@ public:
Java：
```java
class Solution {
public int maxProfit(int[] prices) {
int sum = 0;
int profit = 0;
int buy = prices[0];
for (int i = 1; i < prices.length; i++) {
profit = prices[i] - buy;
if (profit > 0) {
sum += profit;
}
buy = prices[i];
}
return sum;
}
}
```
Python：
@ -149,4 +165,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

23
problems/0134.加油站.md
View File

@ -199,7 +199,28 @@ public:
Java：
```java
class Solution {
public int canCompleteCircuit(int[] gas, int[] cost) {
int sum = 0;
int min = 0;
for (int i = 0; i < gas.length; i++) {
sum += (gas[i] - cost[i]);
min = Math.min(sum, min);
}
if (sum < 0) return -1;
if (min >= 0) return 0;
for (int i = gas.length - 1; i > 0; i--) {
min += (gas[i] - cost[i]);
if (min >= 0) return i;
}
return -1;
}
}
```
Python：
@ -213,4 +234,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

30
problems/0135.分发糖果.md
View File

@ -130,7 +130,35 @@ public:
Java：
```java
class Solution {
public int candy(int[] ratings) {
int[] candy = new int[ratings.length];
for (int i = 0; i < candy.length; i++) {
candy[i] = 1;
}
for (int i = 1; i < ratings.length; i++) {
if (ratings[i] > ratings[i - 1]) {
candy[i] = candy[i - 1] + 1;
}
}
for (int i = ratings.length - 2; i >= 0; i--) {
if (ratings[i] > ratings[i + 1]) {
candy[i] = Math.max(candy[i],candy[i + 1] + 1);
}
}
int count = 0;
for (int i = 0; i < candy.length; i++) {
count += candy[i];
}
return count;
}
}
```
Python：
@ -144,4 +172,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

18
problems/0139.单词拆分.md
View File

@ -232,7 +232,23 @@ public:
Java：
```java
class Solution {
public boolean wordBreak(String s, List<String> wordDict) {
boolean[] valid = new boolean[s.length() + 1];
valid[0] = true;
for (int i = 1; i <= s.length(); i++) {
for (int j = 0; j < i; j++) {
if (wordDict.contains(s.substring(j,i)) && valid[j]) {
valid[i] = true;
}
}
}
return valid[s.length()];
}
}
```
Python：
@ -246,4 +262,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

28
problems/0142.环形链表II.md
View File

@ -186,7 +186,35 @@ public:
Java：
```java
public class Solution {
public ListNode detectCycle(ListNode head) {
// 1.寻找相遇点
ListNode fast = head;
ListNode slow = head;
while (fast != null && fast.next != null) {
fast = fast.next.next;
slow = slow.next;
if (fast != slow) {
continue;
}
ListNode meet = fast;
// 2.寻找入口点
slow = head;
while (slow != fast) {
slow = slow.next;
fast = fast.next;
}
return fast;
}
return null;
}
}
```
Python：

71
problems/0151.翻转字符串里的单词.md
View File

@ -212,6 +212,77 @@ public:
Java：
```java
class Solution {
public String reverseWords(String s) {
char[] chars = s.toCharArray();
// 1.双指针去除空格
// 去除头尾空格
int head = 0;
while (chars[head] == ' ') {
head ++;
}
int tail = chars.length - 1;
while (chars[tail] == ' ') {
tail --;
}
// 去除中间空格
int p1 = head;
int p2 = head + 1;
while (p2 <= tail) {
if (chars[p2 -1] == ' ' && chars[p2] == ' ') {
p2 ++;
continue;
}
chars[p1 + 1] = chars[p2];
p1 ++;
p2 ++;
}
tail = p1;
// 2.双指针翻转整个字符串
chars = reverse(chars, head, tail);
// 3.双指针翻转每个单词
p1 = head;
p2 = head;
for (int i = head; i <= tail;) {
int add = 0;
while (i + add <= tail && chars[i + add] != ' ') {
add ++;
}
if (i + add != tail) {
reverse(chars, i, i + add - 1);
i += add + 1;
} else {
reverse(chars, i, tail);
i = tail + 1;
}
}
return new String(chars, head, tail - head + 1);
}
char[] reverse(char[] chars, int begin, int end) {
int p1 = begin;
int p2 = end;
while (p1 < p2) {
chars[p1] ^= chars[p2];
chars[p2] ^= chars[p1];
chars[p1] ^= chars[p2];
p1 ++;
p2 --;
}
return chars;
}
}
```
Python：

20
problems/0206.翻转链表.md
View File

@ -102,6 +102,24 @@ public:
Java：
```java
class Solution {
public ListNode reverseList(ListNode head) {
if (head == null || head.next == null) return head;
ListNode last = head;
ListNode cur = head.next;
head.next = null;
while (cur.next != null) {
ListNode tmp = cur.next;
cur.next = last;
last = cur;
cur = tmp;
}
cur.next = last;
return cur;
}
}
```
Python：
@ -116,4 +134,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

20
problems/0209.长度最小的子数组.md
View File

@ -148,7 +148,25 @@ class Solution:
Java：
```java
class Solution {
// 滑动窗口
public int minSubArrayLen(int s, int[] nums) {
int left = 0;
int sum = 0;
int result = Integer.MAX_VALUE;
for (int right = 0; right < nums.length; right++) {
sum += nums[right];
while (sum >= s) {
result = Math.min(result, right - left + 1);
sum -= nums[left++];
}
}
return result == Integer.MAX_VALUE ? 0 : result;
}
}
```
Python：
@ -177,4 +195,4 @@ var minSubArrayLen = (target, nums) => {
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

3
problems/0216.组合总和III.md
View File

@ -257,6 +257,7 @@ class Solution {
list.remove(list.size() - 1);
backtracking(k, n, maxNum - 1);
}
}
```
@ -272,4 +273,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

13
problems/0222.完全二叉树的节点个数.md
View File

@ -194,7 +194,18 @@ public:
Java：
```java
class Solution {
public int countNodes(TreeNode root) {
if (root == null) return 0;
int leftnum = countNodes(root.left);
int rightnum = countNodes(root.right);
return leftnum + rightnum + 1;
}
}
```
Python：
@ -208,4 +219,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

20
problems/0226.翻转二叉树.md
View File

@ -203,7 +203,25 @@ public:
Java：
```java
class Solution {
public TreeNode invertTree(TreeNode root) {
invert(root);
return root;
}
private static void invert (TreeNode root) {
if (root == null) return;
invert(root.left);
TreeNode t = root.left;
root.left = root.right;
root.right = t;
invert(root.left);
}
}
```
Python：
@ -230,4 +248,4 @@ func invertTree(root *TreeNode) *TreeNode {
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

21
problems/0235.二叉搜索树的最近公共祖先.md
View File

@ -29,7 +29,7 @@
输入: root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 4
输出: 2
解释: 节点 2 和节点 4 的最近公共祖先是 2, 因为根据定义最近公共祖先节点可以为节点本身。
 
说明:
@ -229,7 +229,22 @@ public:
Java：
```java
class Solution {
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
while (true) {
if (root.val > p.val && root.val > q.val) {
root = root.left;
} else if (root.val < p.val && root.val < q.val) {
root = root.right;
} else {
break;
}
}
return root;
}
}
```
Python：
@ -243,4 +258,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

17
problems/0236.二叉树的最近公共祖先.md
View File

@ -223,7 +223,20 @@ public:
Java：
```java
class Solution {
TreeNode pre;
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
if (root == null || root.val == p.val ||root.val == q.val) return root;
TreeNode left = lowestCommonAncestor(root.left,p,q);
TreeNode right = lowestCommonAncestor(root.right,p,q);
if (left != null && right != null) return root;
else if (left == null && right != null) return right;
else if (left != null && right == null) return left;
else return null;
}
}
```
Python：
@ -237,4 +250,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

3
problems/0242.有效的字母异位词.md
View File

@ -88,6 +88,7 @@ Java：
```java
class Solution {
public boolean isAnagram(String s, String t) {
int[] record = new int[26];
for (char c : s.toCharArray()) {
record[c - 'a'] += 1;
@ -138,4 +139,4 @@ func isAnagram(s string, t string) bool {
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

35
problems/0257.二叉树的所有路径.md
View File

@ -280,8 +280,39 @@ public:
## 其他语言版本
Java：
```java
class Solution {
public List<String> binaryTreePaths(TreeNode root) {
LinkedList<TreeNode> stack = new LinkedList<>();
List<String> list = new LinkedList<>();
TreePaths(root,stack,list);
return list;
}
private static void TreePaths (TreeNode root, LinkedList<TreeNode> path, List<String> res) {
path.add(root);
if (root.left == null && root.right == null) {
StringBuilder sb = new StringBuilder();
for (TreeNode n : path) {
sb.append(n.val);
sb.append("->");
}
sb.delete(sb.length()-2,sb.length());
res.add(sb.toString());
return;
}
if (root.left != null) {
TreePaths(root.left, path, res);
path.removeLast();
}
if (root.right != null) {
TreePaths(root.right, path, res);
path.removeLast();
}
}
}
```
Python：
@ -296,4 +327,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

52
problems/0347.前K个高频元素.md
View File

@ -133,7 +133,59 @@ public:
Java：
```java
public class N0347 {
/**
* 解法：
* 1.统计频次。O(n)
* 2.排序。O(nlogn)
* 3.取前K个元素
*
* 注意到，排序的时候需要用小顶堆，而不是大顶堆。因为每次需要把最小的堆顶弹出去，最后才剩下最大的k个。
* 时间复杂度：O(n + nlogk) = O(nlogk)
*/
public int[] topKFrequent(int[] nums, int k) {
HashMap<Integer, Integer> map = statistic(nums);
PriorityQueue<Integer> pq = new PriorityQueue<>(new Comparator<Integer>() {
@Override
public int compare(Integer o1, Integer o2) {
return map.get(o1) - map.get(o2);
}
});
for (Integer key : map.keySet()) {
if (pq.size() < k) {
pq.offer(key);
} else if (map.get(pq.peek()) < map.get(key)){
pq.poll();
pq.offer(key);
}
}
int[] result = new int[k];
for (int i = 0; i < k; i++) {
result[i] = pq.poll();
}
return result;
}
// key: 值，value：次数
private HashMap<Integer, Integer> statistic(int[] nums) {
HashMap<Integer, Integer> map = new HashMap<>();
for (int num : nums) {
if (map.get(num) == null) {
map.put(num, 1);
} else {
map.put(num, map.get(num) + 1);
}
}
return map;
}
}
```
Python：

18
problems/0377.组合总和Ⅳ.md
View File

@ -147,6 +147,7 @@ C++测试用例有超过两个树相加超过int的数据，所以需要在if里
Java：
```Java
class Solution {
public int combinationSum4(int[] nums, int target) {
@ -163,10 +164,23 @@ class Solution {
}
}
```
Python：
```python
class Solution:
def combinationSum4(self, nums, target):
dp = [0] * (target + 1)
dp[0] = 1
for i in range(1, target+1):
for j in nums:
if i >= j:
dp[i] += dp[i - j]
return dp[-1]
```
Go：
@ -177,4 +191,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

2
problems/0404.左叶子之和.md
View File

@ -204,7 +204,6 @@ class Solution {
Python：
@ -217,5 +216,6 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

25
problems/0406.根据身高重建队列.md
View File

@ -185,7 +185,30 @@ public:
Java：
```java
class Solution {
public int[][] reconstructQueue(int[][] people) {
Arrays.sort(people, new Comparator<int[]>() {
@Override
public int compare(int[] o1, int[] o2) {
if (o1[0] != o2[0]) {
return Integer.compare(o2[0],o1[0]);
} else {
return Integer.compare(o1[1],o2[1]);
}
}
});
LinkedList<int[]> que = new LinkedList<>();
for (int[] p : people) {
que.add(p[1],p);
}
return que.toArray(new int[people.length][]);
}
}
```
Python：
@ -199,4 +222,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

29
problems/0435.无重叠区间.md
View File

@ -182,7 +182,34 @@ public:
Java：
```java
class Solution {
public int eraseOverlapIntervals(int[][] intervals) {
if (intervals.length < 2) return 0;
Arrays.sort(intervals, new Comparator<int[]>() {
@Override
public int compare(int[] o1, int[] o2) {
if (o1[0] != o2[0]) {
return Integer.compare(o1[1],o2[1]);
} else {
return Integer.compare(o2[0],o1[0]);
}
}
});
int count = 0;
int edge = intervals[0][1];
for (int i = 1; i < intervals.length; i++) {
if (intervals[i][0] < edge) {
count++;
} else {
edge = intervals[i][1];
}
}
return count;
}
}
```
Python：
@ -196,4 +223,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

29
problems/0450.删除二叉搜索树中的节点.md
View File

@ -251,7 +251,34 @@ public:
Java：
```java
class Solution {
public TreeNode deleteNode(TreeNode root, int key) {
root = delete(root,key);
return root;
}
private TreeNode delete(TreeNode root, int key) {
if (root == null) return null;
if (root.val > key) {
root.left = delete(root.left,key);
} else if (root.val < key) {
root.right = delete(root.right,key);
} else {
if (root.left == null) return root.right;
if (root.right == null) return root.left;
TreeNode tmp = root.right;
while (tmp.left != null) {
tmp = tmp.left;
}
root.val = tmp.val;
root.right = delete(root.right,tmp.val);
}
return root;
}
}
```
Python：
@ -303,4 +330,4 @@ func deleteNode1(root *TreeNode)*TreeNode{
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

27
problems/0452.用最少数量的箭引爆气球.md
View File

@ -139,7 +139,32 @@ public:
Java：
```java
class Solution {
public int findMinArrowShots(int[][] points) {
Arrays.sort(points, new Comparator<int[]>() {
@Override
public int compare(int[] o1, int[] o2) {
if (o1[0] != o2[0]) {
return Integer.compare(o1[0],o2[0]);
} else {
return Integer.compare(o1[0],o2[0]);
}
}
});
int count = 1;
for (int i = 1; i < points.length; i++) {
if (points[i][0] > points[i - 1][1]) {
count++;
} else {
points[i][1] = Math.min(points[i][1],points[i - 1][1]);
}
}
return count;
}
}
```
Python：
@ -153,4 +178,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

22
problems/0455.分发饼干.md
View File

@ -30,7 +30,7 @@
你有两个孩子和三块小饼干，2个孩子的胃口值分别是1,2。
你拥有的饼干数量和尺寸都足以让所有孩子满足。
所以你应该输出2.
 
提示：
* 1 <= g.length <= 3 * 10^4
@ -115,7 +115,23 @@ public:
Java：
```java
class Solution {
public int findContentChildren(int[] g, int[] s) {
Arrays.sort(g);
Arrays.sort(s);
int start = 0;
int count = 0;
for (int i = 0; i < s.length && start < g.length; i++) {
if (s[i] >= g[start]) {
start++;
count++;
}
}
return count;
}
}
```
Python：
@ -129,4 +145,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

28
problems/0491.递增子序列.md
View File

@ -200,6 +200,32 @@ public:
Java：
```java
class Solution {
private List<Integer> path = new ArrayList<>();
private List<List<Integer>> res = new ArrayList<>();
public List<List<Integer>> findSubsequences(int[] nums) {
backtracking(nums,0);
return res;
}
private void backtracking (int[] nums, int start) {
if (path.size() > 1) {
res.add(new ArrayList<>(path));
}
int[] used = new int[201];
for (int i = start; i < nums.length; i++) {
if (!path.isEmpty() && nums[i] < path.get(path.size() - 1) ||
(used[nums[i] + 100] == 1)) continue;
used[nums[i] + 100] = 1;
path.add(nums[i]);
backtracking(nums, i + 1);
path.remove(path.size() - 1);
}
}
}
```
Python：
@ -214,4 +240,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

21
problems/0494.目标和.md
View File

@ -241,7 +241,24 @@ dp[j] += dp[j - nums[i]];
Java：
```java
class Solution {
public int findTargetSumWays(int[] nums, int target) {
int sum = 0;
for (int i = 0; i < nums.length; i++) sum += nums[i];
if ((target + sum) % 2 != 0) return 0;
int size = (target + sum) / 2;
int[] dp = new int[size + 1];
dp[0] = 1;
for (int i = 0; i < nums.length; i++) {
for (int j = size; j >= nums[i]; j--) {
dp[j] += dp[j - nums[i]];
}
}
return dp[size];
}
}
```
Python：
@ -255,4 +272,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

42
problems/0501.二叉搜索树中的众数.md
View File

@ -344,7 +344,47 @@ public:
Java：
```java
class Solution {
private LinkedList<Integer> list = new LinkedList<>();
private int currentValue;
private int count;
private int maxCount;
public int[] findMode(TreeNode root) {
count = 0;
maxCount = 0;
currentValue = root.val;
findModeTrl(root);
int[] res = new int[list.size()];
for (int i = 0; i < res.length; i++) {
res[i] = list.get(i);
}
return res;
}
private void findModeTrl (TreeNode root) {
if (root == null) return;
findModeTrl(root.left);
if (root.val == currentValue) {
count++;
} else {
currentValue = root.val;
count = 1;
}
if (count == maxCount) {
list.add(root.val);
} else if (count > maxCount) {
maxCount = count;
list.clear();
list.add(currentValue);
}
findModeTrl(root.right);
}
}
```
Python：
@ -358,4 +398,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

24
problems/0513.找树左下角的值.md
View File

@ -217,7 +217,29 @@ public:
Java：
```java
class Solution {
private int Deep = -1;
private int value = 0;
public int findBottomLeftValue(TreeNode root) {
value = root.val;
findLeftValue(root,0);
return value;
}
private void findLeftValue (TreeNode root,int deep) {
if (root == null) return;
if (root.left == null && root.right == null) {
if (deep > Deep) {
value = root.val;
Deep = deep;
}
}
if (root.left != null) findLeftValue(root.left,deep + 1);
if (root.right != null) findLeftValue(root.right,deep + 1);
}
}
```
Python：
@ -231,4 +253,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

19
problems/0516.最长回文子序列.md
View File

@ -148,6 +148,25 @@ public:
Java：
```java
public class Solution {
public int longestPalindromeSubseq(String s) {
int len = s.length();
int[][] dp = new int[len + 1][len + 1];
for (int i = len - 1; i >= 0; i--) { // 从后往前遍历 保证情况不漏
dp[i][i] = 1; // 初始化
for (int j = i + 1; j < len; j++) {
if (s.charAt(i) == s.charAt(j)) {
dp[i][j] = dp[i + 1][j - 1] + 2;
} else {
dp[i][j] = Math.max(dp[i + 1][j], Math.max(dp[i][j], dp[i][j - 1]));
}
}
}
return dp[0][len - 1];
}
}
```
Python：

21
problems/0530.二叉搜索树的最小绝对差.md
View File

@ -151,7 +151,26 @@ public:
Java：
```java
class Solution {
private TreeNode pre = null;
private int res = Integer.MAX_VALUE;
public int getMinimumDifference(TreeNode root) {
getMiniDiff(root);
return res;
}
private void getMiniDiff (TreeNode root) {
if (root == null) return;
getMiniDiff(root.left);
if (pre != null) {
res = Math.min(root.val - pre.val,res);
}
pre = root;
getMiniDiff(root.right);
}
}
```
Python：
@ -165,4 +184,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

18
problems/0538.把二叉搜索树转换为累加树.md
View File

@ -173,7 +173,23 @@ public:
Java：
```java
class Solution {
private int count = 0;
public TreeNode convertBST(TreeNode root) {
convert(root);
return root;
}
private void convert (TreeNode root) {
if (root == null) return;
convert(root.right);
count += root.val;
root.val = count;
convert(root.left);
}
}
```
Python：
@ -187,4 +203,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

14
problems/0617.合并二叉树.md
View File

@ -256,7 +256,19 @@ public:
Java：
```java
class Solution {
public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
if (root1 == null) return root2;
if (root2 == null) return root1;
TreeNode newRoot = new TreeNode(root1.val + root2.val);
newRoot.left = mergeTrees(root1.left,root2.left);
newRoot.right = mergeTrees(root1.right,root2.right);
return newRoot;
}
}
```
Python：
@ -270,4 +282,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

26
problems/0654.最大二叉树.md
View File

@ -224,7 +224,31 @@ root->right = traversal(nums, maxValueIndex + 1, right);
Java：
```java
class Solution {
public TreeNode constructMaximumBinaryTree(int[] nums) {
if (nums.length == 0) return null;
return constructMaximumBinaryTree(nums,0,nums.length);
}
private TreeNode constructMaximumBinaryTree(int[] nums, int begin, int end) {
if (begin == end) return null;
int rootValue = nums[begin];
int index = begin;
for (int i = begin; i < end ; i++) {
if (nums[i] > rootValue) {
rootValue = nums[i];
index = i;
}
}
TreeNode root = new TreeNode(rootValue);
root.left = constructMaximumBinaryTree(nums, begin,index);
root.right = constructMaximumBinaryTree(nums,index+1,end);
return root;
}
}
```
Python：
@ -238,4 +262,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

25
problems/0669.修剪二叉搜索树.md
View File

@ -242,7 +242,30 @@ public:
Java：
```java
class Solution {
public TreeNode trimBST(TreeNode root, int low, int high) {
root = trim(root,low,high);
return root;
}
private static TreeNode trim(TreeNode root,int low, int high) {
if (root == null ) return null;
if (root.val < low) {
return trim(root.right,low,high);
}
if (root.val > high) {
return trim(root.left,low,high);
}
root.left = trim(root.left,low,high);
root.right = trim(root.right,low,high);
return root;
}
}
```
Python：
@ -256,4 +279,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

53
problems/0700.二叉搜索树中的搜索.md
View File

@ -140,12 +140,61 @@ public:
## 其他语言版本
Java：
递归法：
```java
class Solution {
public TreeNode searchBST(TreeNode root, int val) {
if (root == null) return null;
if (root.val == val) return root;
else if (root.val > val) return searchBST(root.left, val);
else return searchBST(root.right, val);
}
}
```
迭代法：
```java
class Solution {
public TreeNode searchBST(TreeNode root, int val) {
while (root != null)
if (val < root.val) root = root.left;
else if (val > root.val) root = root.right;
else return root;
return root;
}
}
```
Python：
递归法：
```python
class Solution:
def searchBST(self, root: TreeNode, val: int) -> TreeNode:
if root is None:
return None
if val < root.val: return self.searchBST(root.left, val)
elif val > root.val: return self.searchBST(root.right, val)
else: return root
```
迭代法：
```python
class Solution:
def searchBST(self, root: TreeNode, val: int) -> TreeNode:
while root is not None:
if val < root.val: root = root.left
elif val > root.val: root = root.right
else: return root
return root
```
Go：
@ -156,4 +205,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

63
problems/0701.二叉搜索树中的插入操作.md
View File

@ -16,7 +16,7 @@
注意，可能存在多种有效的插入方式，只要树在插入后仍保持为二叉搜索树即可。 你可以返回任意有效的结果。
![701.二叉搜索树中的插入操作](https://img-blog.csdnimg.cn/20201019173259554.png)
 
提示：
* 给定的树上的节点数介于 0 和 10^4 之间
@ -206,12 +206,69 @@ public:
## 其他语言版本
Java：
```java
class Solution {
public TreeNode insertIntoBST(TreeNode root, int val) {
if (root == null) return new TreeNode(val);
TreeNode newRoot = root;
TreeNode pre = root;
while (root != null) {
pre = root;
if (root.val > val) {
root = root.left;
} else if (root.val < val) {
root = root.right;
}
}
if (pre.val > val) {
pre.left = new TreeNode(val);
} else {
pre.right = new TreeNode(val);
}
return newRoot;
}
}
```
递归法
```java
class Solution {
public TreeNode insertIntoBST(TreeNode root, int val) {
return buildTree(root, val);
}
public TreeNode buildTree(TreeNode root, int val){
if (root == null) // 如果当前节点为空，也就意味着val找到了合适的位置，此时创建节点直接返回。
return new TreeNode(val);
if (root.val < val){
root.right = buildTree(root.right, val); // 递归创建右子树
}else if (root.val > val){
root.left = buildTree(root.left, val); // 递归创建左子树
}
return root;
}
}
```
Python：
递归法
```python
class Solution:
def insertIntoBST(self, root: TreeNode, val: int) -> TreeNode:
if root is None:
return TreeNode(val) # 如果当前节点为空，也就意味着val找到了合适的位置，此时创建节点直接返回。
if root.val < val:
root.right = self.insertIntoBST(root.right, val) # 递归创建右子树
if root.val > val:
root.left = self.insertIntoBST(root.left, val) # 递归创建左子树
return root
```
Go：
@ -222,4 +279,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

45
problems/0704.二分查找.md
View File

@ -23,7 +23,7 @@
输入: nums = [-1,0,3,5,9,12], target = 2
输出: -1
解释: 2 不存在 nums 中因此返回 -1
 
提示：
* 你可以假设 nums 中的所有元素是不重复的。
@ -146,11 +146,50 @@ public:
## 其他语言版本
Java：
（版本一）左闭右闭区间
```java
class Solution {
public int search(int[] nums, int target) {
int left = 0, right = nums.length - 1;
while (left <= right) {
int mid = left + ((right - left) >> 1);
if (nums[mid] == target)
return mid;
else if (nums[mid] < target)
left = mid + 1;
else if (nums[mid] > target)
right = mid - 1;
}
return -1;
}
}
```
（版本二）左闭右开区间
```java
class Solution {
public int search(int[] nums, int target) {
int left = 0, right = nums.length;
while (left < right) {
int mid = left + ((right - left) >> 1);
if (nums[mid] == target)
return mid;
else if (nums[mid] < target)
left = mid + 1;
else if (nums[mid] > target)
right = mid;
}
return -1;
}
}
```
Python：
```python3
class Solution:
def search(self, nums: List[int], target: int) -> int:
@ -178,4 +217,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

18
problems/0714.买卖股票的最佳时机含手续费.md
View File

@ -156,7 +156,23 @@ public:
Java：
```java
class Solution {
public int maxProfit(int[] prices, int fee) {
int buy = prices[0] + fee;
int sum = 0;
for (int p : prices) {
if (p + fee < buy) {
buy = p + fee;
} else if (p > buy){
sum += p - buy;
buy = p;
}
}
return sum;
}
}
```
Python：

20
problems/0738.单调递增的数字.md
View File

@ -125,6 +125,24 @@ public:
Java：
```java
class Solution {
public int monotoneIncreasingDigits(int N) {
String[] strings = (N + "").split("");
int start = strings.length;
for (int i = strings.length - 1; i > 0; i--) {
if (Integer.parseInt(strings[i]) < Integer.parseInt(strings[i - 1])) {
strings[i - 1] = (Integer.parseInt(strings[i - 1]) - 1) + "";
start = i;
}
}
for (int i = start; i < strings.length; i++) {
strings[i] = "9";
}
return Integer.parseInt(String.join("",strings));
}
}
```
Python：
@ -139,4 +157,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

23
problems/0763.划分字母区间.md
View File

@ -84,7 +84,28 @@ public:
Java：
```java
class Solution {
public List<Integer> partitionLabels(String S) {
List<Integer> list = new LinkedList<>();
int[] edge = new int[123];
char[] chars = S.toCharArray();
for (int i = 0; i < chars.length; i++) {
edge[chars[i] - 0] = i;
}
int idx = 0;
int last = -1;
for (int i = 0; i < chars.length; i++) {
idx = Math.max(idx,edge[chars[i] - 0]);
if (i == idx) {
list.add(i - last);
last = i;
}
}
return list;
}
}
```
Python：

28
problems/0860.柠檬水找零.md
View File

@ -127,7 +127,33 @@ public:
Java：
```java
class Solution {
public boolean lemonadeChange(int[] bills) {
int cash_5 = 0;
int cash_10 = 0;
for (int i = 0; i < bills.length; i++) {
if (bills[i] == 5) {
cash_5++;
} else if (bills[i] == 10) {
cash_5--;
cash_10++;
} else if (bills[i] == 20) {
if (cash_10 > 0) {
cash_10--;
cash_5--;
} else {
cash_5 -= 3;
}
}
if (cash_5 < 0 || cash_10 < 0) return false;
}
return true;
}
}
```
Python：
@ -141,4 +167,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

29
problems/0968.监控二叉树.md
View File

@ -316,6 +316,33 @@ public:
Java：
```java
class Solution {
private int count = 0;
public int minCameraCover(TreeNode root) {
if (trval(root) == 0) count++;
return count;
}
private int trval(TreeNode root) {
if (root == null) return -1;
int left = trval(root.left);
int right = trval(root.right);
if (left == 0 || right == 0) {
count++;
return 2;
}
if (left == 2 || right == 2) {
return 1;
}
return 0;
}
}
```
Python：
@ -330,4 +357,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

26
problems/1005.K次取反后最大化的数组和.md
View File

@ -29,7 +29,7 @@
输入：A = [2,-3,-1,5,-4], K = 2
输出：13
解释：选择索引 (1, 4) ，然后 A 变为 [2,3,-1,5,4]。
 
提示：
* 1 <= A.length <= 10000
@ -99,7 +99,29 @@ public:
Java：
```java
class Solution {
public int largestSumAfterKNegations(int[] A, int K) {
if (A.length == 1) return A[0];
Arrays.sort(A);
int sum = 0;
int idx = 0;
for (int i = 0; i < K; i++) {
if (i < A.length - 1 && A[idx] < 0) {
A[idx] = -A[idx];
if (A[idx] >= Math.abs(A[idx + 1])) idx++;
continue;
}
A[idx] = -A[idx];
}
for (int i = 0; i < A.length; i++) {
sum += A[i];
}
return sum;
}
}
```
Python：
@ -113,4 +135,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>

38
problems/1143.最长公共子序列.md
View File

@ -31,7 +31,7 @@
输入：text1 = "abc", text2 = "def"
输出：0
解释：两个字符串没有公共子序列，返回 0。
 
提示:
* 1 <= text1.length <= 1000
* 1 <= text2.length <= 1000
@ -126,12 +126,44 @@ public:
## 其他语言版本
Java：
```java
class Solution {
public int longestCommonSubsequence(String text1, String text2) {
int[][] dp = new int[text1.length() + 1][text2.length() + 1]; // 先对dp数组做初始化操作
for (int i = 1 ; i <= text1.length() ; i++) {
char char1 = text1.charAt(i - 1);
for (int j = 1; j <= text2.length(); j++) {
char char2 = text2.charAt(j - 1);
if (char1 == char2) { // 开始列出状态转移方程
dp[i][j] = dp[i - 1][j - 1] + 1;
} else {
dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
}
}
}
return dp[text1.length()][text2.length()];
}
}
```
Python：
```python
class Solution:
def longestCommonSubsequence(self, text1: str, text2: str) -> int:
len1, len2 = len(text1)+1, len(text2)+1
dp = [[0 for _ in range(len1)] for _ in range(len2)] # 先对dp数组做初始化操作
for i in range(1, len2):
for j in range(1, len1): # 开始列出状态转移方程
if text1[j-1] == text2[i-1]:
dp[i][j] = dp[i-1][j-1]+1
else:
dp[i][j] = max(dp[i-1][j], dp[i][j-1])
return dp[-1][-1]
```
Go：
@ -142,4 +174,4 @@ Go：
* 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)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>