Merge branch 'youngyangyang04:master' into master

This commit is contained in:
gaoyangu
2021-12-20 10:42:37 +08:00
committed by GitHub
3 changed files with 105 additions and 3 deletions

View File

@ -894,7 +894,58 @@ var strStr = function (haystack, needle) {
};
```
Swift 版本
> 前缀表统一减一
```swift
func strStr(_ haystack: String, _ needle: String) -> Int {
let s = Array(haystack), p = Array(needle)
guard p.count != 0 else { return 0 }
// 2 pointer
var j = -1
var next = [Int](repeating: -1, count: needle.count)
// KMP
getNext(&next, needle: p)
for i in 0 ..< s.count {
while j >= 0 && s[i] != p[j + 1] {
//不匹配之后寻找之前匹配的位置
j = next[j]
}
if s[i] == p[j + 1] {
//匹配,双指针同时后移
j += 1
}
if j == (p.count - 1) {
//出现匹配字符串
return i - p.count + 1
}
}
return -1
}
//前缀表统一减一
func getNext(_ next: inout [Int], needle: [Character]) {
var j: Int = -1
next[0] = j
// i 从 1 开始
for i in 1 ..< needle.count {
while j >= 0 && needle[i] != needle[j + 1] {
j = next[j]
}
if needle[i] == needle[j + 1] {
j += 1;
}
next[i] = j
}
print(next)
}
```
-----------------------
<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

View File

@ -405,7 +405,7 @@ class Solution:
if len(path) == k:
res.append(path[:])
return
for i in range(StartIndex, n-(k-len(path)) + 2):
for i in range(StartIndex, n + 1):
path.append(i)
backtrack(n, k, i+1)
path.pop()
@ -414,7 +414,7 @@ class Solution:
```
剪枝:
```python3
```python
class Solution:
def combine(self, n: int, k: int) -> List[List[int]]:
res=[] #存放符合条件结果的集合
@ -423,7 +423,7 @@ class Solution:
if len(path) == k:
res.append(path[:])
return
for i in range(startIndex,n-(k-len(path))+2): #优化的地方
for i in range(startIndex,n - (k - len(path)) + 2): #优化的地方
path.append(i) #处理节点
backtrack(n,k,i+1) #递归
path.pop() #回溯,撤销处理的节点

View File

@ -409,5 +409,56 @@ int* postorderTraversal(struct TreeNode* root, int* returnSize){
}
```
Swift:
前序遍历144.二叉树的前序遍历)
```Swift
func preorderTraversal(_ root: TreeNode?) -> [Int] {
var res = [Int]()
preorder(root, res: &res)
return res
}
func preorder(_ root: TreeNode?, res: inout [Int]) {
if root == nil {
return
}
res.append(root!.val)
preorder(root!.left, res: &res)
preorder(root!.right, res: &res)
}
```
中序遍历94. 二叉树的中序遍历)
```Swift
func inorderTraversal(_ root: TreeNode?) -> [Int] {
var res = [Int]()
inorder(root, res: &res)
return res
}
func inorder(_ root: TreeNode?, res: inout [Int]) {
if root == nil {
return
}
inorder(root!.left, res: &res)
res.append(root!.val)
inorder(root!.right, res: &res)
}
```
后序遍历145. 二叉树的后序遍历)
```Swift
func postorderTraversal(_ root: TreeNode?) -> [Int] {
var res = [Int]()
postorder(root, res: &res)
return res
}
func postorder(_ root: TreeNode?, res: inout [Int]) {
if root == nil {
return
}
postorder(root!.left, res: &res)
postorder(root!.right, res: &res)
res.append(root!.val)
}
```
-----------------------
<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>