Merge branch 'master' into remote

Author: youngyangyang04

README.md

@@ -1,4 +1,4 @@
-👉 推荐 [在线阅读](http://programmercarl.com/) (Github在国内访问经常不稳定)
+👉 推荐 [在线阅读](http://programmercarl.com/) (Github在国内访问经常不稳定)         
 👉 推荐 [Gitee同步](https://gitee.com/programmercarl/leetcode-master) 
 
 > 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)
@@ -494,6 +494,7 @@
 ## 图论
 * [463.岛屿的周长](./problems/0463.岛屿的周长.md) （模拟）
 * [841.钥匙和房间](./problems/0841.钥匙和房间.md) 【有向图】dfs，bfs都可以
+* [127.单词接龙](./problems/0127.单词接龙.md) 广搜
 
 ## 并查集 
 * [684.冗余连接](./problems/0684.冗余连接.md) 【并查集基础题目】

problems/0001.两数之和.md

@@ -206,6 +206,23 @@ function twoSum(array $nums, int $target): array
 }
 ```
 
+Swift：
+```swift
+func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
+    var res = [Int]()
+    var dict = [Int : Int]()
+    for i in 0 ..< nums.count {
+        let other = target - nums[i]
+        if dict.keys.contains(other) {
+            res.append(i)
+            res.append(dict[other]!)
+            return res
+        }
+        dict[nums[i]] = i
+    }
+    return res
+}
+```
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)

problems/0027.移除元素.md

@@ -246,6 +246,30 @@ func removeElement(_ nums: inout [Int], _ val: Int) -> Int {
 }
 ```
 
+PHP:
+```php
+class Solution {
+    /**
+     * @param Integer[] $nums
+     * @param Integer $val
+     * @return Integer
+     */
+    function removeElement(&$nums, $val) {
+        if (count($nums) == 0) {
+            return 0;
+        }
+        // 快慢指针
+        $slow = 0;
+        for ($fast = 0; $fast < count($nums); $fast++) {
+            if ($nums[$fast] != $val) {
+                $nums[$slow] = $nums[$fast];
+                $slow++;
+            }
+        }
+        return $slow;
+    }
+```
+
 C:
 ```c
 int removeElement(int* nums, int numsSize, int val){

problems/0046.全排列.md

@@ -183,6 +183,32 @@ class Solution {
     }
 }
 ```
+```java
+// 解法2：通过判断path中是否存在数字，排除已经选择的数字
+class Solution {
+    List<List<Integer>> result = new ArrayList<>();
+    LinkedList<Integer> path = new LinkedList<>();
+    public List<List<Integer>> permute(int[] nums) {
+        if (nums.length == 0) return result;
+        backtrack(nums, path);
+        return result;
+    }
+    public void backtrack(int[] nums, LinkedList<Integer> path) {
+        if (path.size() == nums.length) {
+            result.add(new ArrayList<>(path));
+        }
+        for (int i =0; i < nums.length; i++) {
+            // 如果path中已有，则跳过
+            if (path.contains(nums[i])) {
+                continue;
+            } 
+            path.add(nums[i]);
+            backtrack(nums, path);
+            path.removeLast();
+        }
+    }
+}
+```
 
 Python：
 ```python3

problems/0056.合并区间.md

@@ -157,6 +157,28 @@ class Solution {
     }
 }
 ```
+```java
+// 版本2
+class Solution {
+    public int[][] merge(int[][] intervals) {
+        LinkedList<int[]> res = new LinkedList<>();
+        Arrays.sort(intervals, (o1, o2) -> Integer.compare(o1[0], o2[0]));
+        res.add(intervals[0]);
+        for (int i = 1; i < intervals.length; i++) {
+            if (intervals[i][0] <= res.getLast()[1]) {
+                int start = res.getLast()[0];
+                int end = Math.max(intervals[i][1], res.getLast()[1]);
+                res.removeLast();
+                res.add(new int[]{start, end});
+            }
+            else {
+                res.add(intervals[i]);
+            }         
+        }
+        return res.toArray(new int[res.size()][]);
+    }
+}
+```
 
 Python：
 ```python

problems/0059.螺旋矩阵II.md

@@ -191,33 +191,48 @@ class Solution {
 
 python:
 
-```python
+```python3
 class Solution:
+
     def generateMatrix(self, n: int) -> List[List[int]]:
-        left, right, up, down = 0, n-1, 0, n-1
-        matrix = [ [0]*n for _ in range(n)]
-        num = 1
-        while left<=right and up<=down:
-            # 填充左到右
-            for i in range(left, right+1):
-                matrix[up][i] = num
-                num += 1
-            up += 1
-            # 填充上到下
-            for i in range(up, down+1):
-                matrix[i][right] = num
-                num += 1
+        # 初始化要填充的正方形
+        matrix = [[0] * n for _ in range(n)]
+
+        left, right, up, down = 0, n - 1, 0, n - 1
+        number = 1  # 要填充的数字
+
+        while left < right and up < down:
+
+            # 从左到右填充上边
+            for x in range(left, right):
+                matrix[up][x] = number
+                number += 1
+
+            # 从上到下填充右边
+            for y in range(up, down):
+                matrix[y][right] = number
+                number += 1
+
+            # 从右到左填充下边
+            for x in range(right, left, -1):
+                matrix[down][x] = number
+                number += 1
+
+            # 从下到上填充左边
+            for y in range(down, up, -1):
+                matrix[y][left] = number
+                number += 1
+
+            # 缩小要填充的范围
+            left += 1
             right -= 1
-            # 填充右到左
-            for i in range(right, left-1, -1):
-                matrix[down][i] = num
-                num += 1
+            up += 1
             down -= 1
-            # 填充下到上
-            for i in range(down, up-1, -1):
-                matrix[i][left] = num
-                num += 1
-            left += 1
+
+        # 如果阶数为奇数，额外填充一次中心
+        if n % 2:
+            matrix[n // 2][n // 2] = number
+
         return matrix
 ```
 
@@ -358,6 +373,100 @@ func generateMatrix(_ n: Int) -> [[Int]] {
 }
 ```
 
+Rust:
+
+```rust
+impl Solution {
+    pub fn generate_matrix(n: i32) -> Vec<Vec<i32>> {
+        let mut res = vec![vec![0; n as usize]; n as usize];
+        let (mut startX, mut startY, mut offset): (usize, usize, usize) = (0, 0, 1);
+        let mut loopIdx = n/2;
+        let mid: usize = loopIdx as usize;
+        let mut count = 1;
+        let (mut i, mut j): (usize, usize) = (0, 0);
+        while loopIdx > 0 {
+            i = startX;
+            j = startY;
+            
+            while j < (startY + (n as usize) - offset) {
+                res[i][j] = count; 
+                count += 1;
+                j += 1;
+            }
+            
+            while i < (startX + (n as usize) - offset) {
+                res[i][j] = count; 
+                count += 1;
+                i += 1;
+            }
+            
+            while j > startY {
+                res[i][j] = count;
+                count += 1;
+                j -= 1;
+            }
+            
+            while i > startX {
+                res[i][j] = count;
+                count += 1;
+                i -= 1;
+            }
+            
+            startX += 1;
+            startY += 1;   
+            offset += 2; 
+            loopIdx -= 1;
+        }
+        
+        if(n % 2 == 1) {
+            res[mid][mid] = count;
+        }
+        res
+    }
+}
+```
+
+PHP:
+```php
+class Solution {
+    /**
+     * @param Integer $n
+     * @return Integer[][]
+     */
+    function generateMatrix($n) {
+        // 初始化数组
+        $res = array_fill(0, $n, array_fill(0, $n, 0));
+        $mid = $loop = floor($n / 2);
+        $startX = $startY = 0;
+        $offset = 1;
+        $count = 1;
+        while ($loop > 0) {
+            $i = $startX;
+            $j = $startY;
+            for (; $j < $startY + $n - $offset; $j++) {
+                $res[$i][$j] = $count++;
+            }
+            for (; $i < $startX + $n - $offset; $i++) {
+                $res[$i][$j] = $count++;
+            }
+            for (; $j > $startY; $j--) {
+                $res[$i][$j] = $count++;
+            }
+            for (; $i > $startX; $i--) {
+                $res[$i][$j] = $count++;
+            }
+            $startX += 1;
+            $startY += 1;
+            $offset += 2;
+            $loop--;
+        }
+        if ($n % 2 == 1) {
+            $res[$mid][$mid] = $count;
+        }
+        return $res;
+    }
+}
+```
 
 
 -----------------------

problems/0115.不同的子序列.md

@@ -221,6 +221,30 @@ class SolutionDP2:
 ```
 
 Go：
+```go
+func numDistinct(s string, t string) int {
+    dp:= make([][]int,len(s)+1)
+    for i:=0;i<len(dp);i++{
+        dp[i] = make([]int,len(t)+1)
+    }
+    // 初始化
+    for i:=0;i<len(dp);i++{
+        dp[i][0] = 1
+    }
+    // dp[0][j] 为 0，默认值，因此不需要初始化
+    for i:=1;i<len(dp);i++{
+        for j:=1;j<len(dp[i]);j++{
+            if s[i-1] == t[j-1]{
+                dp[i][j] = dp[i-1][j-1] + dp[i-1][j]
+            }else{
+                dp[i][j] = dp[i-1][j]
+            }
+        }
+    }
+    return dp[len(dp)-1][len(dp[0])-1]
+}
+```
+
 
 Javascript:
 ```javascript