diff --git a/problems/0051.N皇后.md b/problems/0051.N皇后.md
index 51415e88..7eb0d7a0 100644
--- a/problems/0051.N皇后.md
+++ b/problems/0051.N皇后.md
@@ -346,69 +346,56 @@ class Solution {
 
 ### Go 
 ```Go
-import "strings"
-var res [][]string
-
-func isValid(board [][]string, row, col int) (res bool){
-    n := len(board)
-    for i:=0; i < row; i++ {
-        if board[i][col] == "Q" {
-            return false
-        }
-    }
-    for i := 0; i < n; i++{
-        if board[row][i] == "Q" {
-            return false
-        }
-    }
-
-    for i ,j := row, col; i >= 0 && j >=0 ; i, j = i - 1, j- 1{
-        if board[i][j] == "Q"{
-            return false
-        }
-    }
-    for i, j := row, col; i >=0 && j < n; i,j = i-1, j+1 {
-        if board[i][j] == "Q" {
-            return false
-        }
-    }
-    return true
-}
-
-func backtrack(board [][]string, row int) {
-    size := len(board)
-    if row == size{
-        temp := make([]string, size)
-        for i := 0; i<size;i++{
-            temp[i] = strings.Join(board[i],"")
-        }
-        res =append(res,temp)
-        return 
-    }
-    for col := 0; col < size; col++ {
-        if !isValid(board, row, col){
-            continue
-        }
-        board[row][col] = "Q"
-        backtrack(board, row+1)
-        board[row][col] = "."
-    }
-}
-
 func solveNQueens(n int) [][]string {
-    res = [][]string{}
-    board := make([][]string, n)
-    for i := 0; i < n; i++{
-        board[i] = make([]string, n)
-    }
-    for i := 0; i < n; i++{
-        for j := 0; j<n;j++{
-            board[i][j] = "."
-        }
-    }
-    backtrack(board, 0)
+    var res [][]string
+	chessboard := make([][]string, n)
+	for i := 0; i < n; i++ {
+		chessboard[i] = make([]string, n)
+	}
+	for i := 0; i < n; i++ {
+		for j := 0; j < n; j++ {
+			chessboard[i][j] = "."
+		}
+	}
+	var backtrack func(int)
+	backtrack = func(row int) {
+		if row == n {
+			temp := make([]string, n)
+			for i, rowStr := range chessboard {
+				temp[i] = strings.Join(rowStr, "")
+			}
+			res = append(res, temp)
+			return
+		}
+		for i := 0; i < n; i++ {
+			if isValid(n, row, i, chessboard) {
+				chessboard[row][i] = "Q"
+				backtrack(row + 1)
+				chessboard[row][i] = "."
+			}
+		}
+	}
+	backtrack(0)
+	return res
+}
 
-    return res
+func isValid(n, row, col int, chessboard [][]string) bool {
+	for i := 0; i < row; i++ {
+		if chessboard[i][col] == "Q" {
+			return false
+		}
+	}
+	for i, j := row-1, col-1; i >= 0 && j >= 0; i, j = i-1, j-1 {
+		if chessboard[i][j] == "Q" {
+			return false
+		}
+	}
+	for i, j := row-1, col+1; i >= 0 && j < n; i, j = i-1, j+1 {
+		if chessboard[i][j] == "Q" {
+			return false
+		}
+	}
+	return true
 }
 ```
 ### Javascript 
diff --git a/problems/0063.不同路径II.md b/problems/0063.不同路径II.md
index 6f405d6a..105b6402 100644
--- a/problems/0063.不同路径II.md
+++ b/problems/0063.不同路径II.md
@@ -266,46 +266,33 @@ Go：
 
 ```go
 func uniquePathsWithObstacles(obstacleGrid [][]int) int {
-	m,n:= len(obstacleGrid),len(obstacleGrid[0])
+	m, n := len(obstacleGrid), len(obstacleGrid[0])
 	// 定义一个dp数组
-	dp := make([][]int,m)
-	for i,_ := range dp {
-		dp[i] = make([]int,n)
+	dp := make([][]int, m)
+	for i, _ := range dp {
+		dp[i] = make([]int, n)
 	}
-	// 初始化
-	for i:=0;i<m;i++ {
-		// 如果是障碍物, 后面的就都是0, 不用循环了
-		if obstacleGrid[i][0] == 1 {
-			break
-		}
-		dp[i][0]=1
+	// 初始化, 如果是障碍物, 后面的就都是0, 不用循环了
+	for i := 0; i < m && obstacleGrid[i][0] == 0; i++ {
+		dp[i][0] = 1
 	}
-	for i:=0;i<n;i++ {
-		if obstacleGrid[0][i] == 1 {
-			break
-		}
-		dp[0][i]=1
+	for i := 0; i < n && obstacleGrid[0][i] == 0; i++ {
+		dp[0][i] = 1
 	}
 	// dp数组推导过程
-	for i:=1;i<m;i++ {
-		for j:=1;j<n;j++ {
-			// 如果obstacleGrid[i][j]这个点是障碍物, 那么我们的dp[i][j]保持为0
-           	 	if obstacleGrid[i][j] != 1 {
+	for i := 1; i < m; i++ {
+		for j := 1; j < n; j++ {
+			// 如果obstacleGrid[i][j]这个点是障碍物, 那么dp[i][j]保持为0
+			if obstacleGrid[i][j] != 1 {
 				// 否则我们需要计算当前点可以到达的路径数
-				dp[i][j] = dp[i-1][j]+dp[i][j-1]
+				dp[i][j] = dp[i-1][j] + dp[i][j-1]
 			}
 		}
 	}
-	// debug遍历dp
-	//for i,_ := range dp {
-	//	for j,_ := range dp[i] {
-	//		fmt.Printf("%.2v,",dp[i][j])
-	//	}
-	//	fmt.Println()
-	//}
 	return dp[m-1][n-1]
 }
 
+
 ```
 
 Javascript
diff --git a/problems/0110.平衡二叉树.md b/problems/0110.平衡二叉树.md
index c0914f05..9d43407a 100644
--- a/problems/0110.平衡二叉树.md
+++ b/problems/0110.平衡二叉树.md
@@ -730,5 +730,33 @@ bool isBalanced(struct TreeNode* root){
 }
 ```
 
+## Swift:
+
+>递归
+```swift
+func isBalanced(_ root: TreeNode?) -> Bool {
+    // -1 已经不是平衡二叉树
+    return getHeight(root) == -1 ? false : true
+}
+func getHeight(_ root: TreeNode?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    let leftHeight = getHeight(root.left)
+    if leftHeight == -1 {
+        return -1
+    }
+    let rightHeight = getHeight(root.right)
+    if rightHeight == -1 {
+        return -1
+    }
+    if abs(leftHeight - rightHeight) > 1 {
+        return -1
+    } else {
+        return 1 + max(leftHeight, rightHeight)
+    }
+}
+```
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>
diff --git a/problems/0151.翻转字符串里的单词.md b/problems/0151.翻转字符串里的单词.md
index d58ace89..ead5fa12 100644
--- a/problems/0151.翻转字符串里的单词.md
+++ b/problems/0151.翻转字符串里的单词.md
@@ -553,6 +553,65 @@ function reverse(strArr, start, end) {
 }
 ```
 
+TypeScript：
+
+```typescript
+function reverseWords(s: string): string {
+    /** Utils **/
+    // 删除多余空格, 如'   hello     world   ' => 'hello world'
+    function delExtraSpace(arr: string[]): void {
+        let left: number = 0,
+            right: number = 0,
+            length: number = arr.length;
+        while (right < length && arr[right] === ' ') {
+            right++;
+        }
+        while (right < length) {
+            if (arr[right] === ' ' && arr[right - 1] === ' ') {
+                right++;
+                continue;
+            }
+            arr[left++] = arr[right++];
+        }
+        if (arr[left - 1] === ' ') {
+            arr.length = left - 1;
+        } else {
+            arr.length = left;
+        }
+    }
+    // 翻转字符串，如：'hello' => 'olleh'
+    function reverseWords(strArr: string[], start: number, end: number) {
+        let temp: string;
+        while (start < end) {
+            temp = strArr[start];
+            strArr[start] = strArr[end];
+            strArr[end] = temp;
+            start++;
+            end--;
+        }
+    }
+
+    /** Main code **/
+    let strArr: string[] = s.split('');
+    delExtraSpace(strArr);
+    let length: number = strArr.length;
+    // 翻转整个字符串
+    reverseWords(strArr, 0, length - 1);
+    let start: number = 0,
+        end: number = 0;
+    while (start < length) {
+        end = start;
+        while (strArr[end] !== ' ' && end < length) {
+            end++;
+        }
+        // 翻转单个单词
+        reverseWords(strArr, start, end - 1);
+        start = end + 1;
+    }
+    return strArr.join('');
+};
+```
+
 Swift:
 
 ```swift
diff --git a/problems/0257.二叉树的所有路径.md b/problems/0257.二叉树的所有路径.md
index cb837d87..7b5fc2e9 100644
--- a/problems/0257.二叉树的所有路径.md
+++ b/problems/0257.二叉树的所有路径.md
@@ -581,7 +581,72 @@ var binaryTreePaths = function(root) {
 };  
 ```
 
+Swift:
 
+> 递归/回溯
+```swift
+func binaryTreePaths(_ root: TreeNode?) -> [String] {
+    var res = [String]()
+    guard let root = root else {
+        return res
+    }
+    var path = [Int]()
+    _binaryTreePaths(root, path: &path, res: &res)
+    return res
+}
+func _binaryTreePaths(_ root: TreeNode, path: inout [Int], res: inout [String]) {
+    path.append(root.val)
+    if root.left ==  nil && root.right == nil {
+        var str = ""
+        for i in 0 ..< path.count - 1 {
+            str.append("\(path[i])->")
+        }
+        str.append("\(path.last!)")
+        res.append(str)
+        return
+    }
+    if let left = root.left {
+        _binaryTreePaths(left, path: &path, res: &res)
+        path.removeLast()
+    }
+    if let right = root.right {
+        _binaryTreePaths(right, path: &path, res: &res)
+        path.removeLast()
+    }
+}
+```
+
+> 迭代
+```swift
+func binaryTreePaths(_ root: TreeNode?) -> [String] {
+    var res = [String]()
+    guard let root = root else {
+        return res
+    }
+    var stackNode = [TreeNode]()
+    stackNode.append(root)
+    
+    var stackStr = [String]()
+    stackStr.append("\(root.val)")
+    
+    while !stackNode.isEmpty {
+        let node = stackNode.popLast()!
+        let str = stackStr.popLast()!
+        if node.left == nil && node.right == nil {
+            res.append(str)
+        }
+        if let left = node.left {
+            stackNode.append(left)
+            stackStr.append("\(str)->\(left.val)")
+        }
+        if let right = node.right {
+            stackNode.append(right)
+            stackStr.append("\(str)->\(right.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>
diff --git a/problems/0494.目标和.md b/problems/0494.目标和.md
index 1835f498..0faef4a5 100644
--- a/problems/0494.目标和.md
+++ b/problems/0494.目标和.md
@@ -289,7 +289,7 @@ func findTargetSumWays(nums []int, target int) int {
 	for _, v := range nums {
 		sum += v
 	}
-	if target > sum {
+	if abs(target) > sum {
 		return 0
 	}
 	if (sum+target)%2 == 1 {
@@ -311,49 +311,12 @@ func findTargetSumWays(nums []int, target int) int {
 	}
 	return dp[bag]
 }
-```
-> 更新版，上一个跑不通了，因为会存在bag 小于0的情况
 
-```go
-func findTargetSumWays(nums []int, target int) int {
-    //先转化为数学问题
-    //a-b=target
-    //a+b=sum
-    //a=(target+sum)/2
-    //求出sum
-    var sum int
-    for _,value:=range nums{
-        sum+=value
-    }
-    //如果sum<target或者 sum+target不是偶数（因为a是int） 或者两者之和小于0了
-    if sum<target||(sum+target)%2==1||(sum+target)<0{
-        return 0
-    }
-    //开始dp初始化
-    dp:=make([][]int,len(nums)+1)
-    for i:=0;i<=len(nums);i++{
-        tmp:=make([]int,(target+sum)/2+1)//背包容量
-        dp[i]=tmp
-    }
-    dp[0][0]=1//当背包容量为0，且物品为0时，填满背包就1种方法
-    for i:=0;i<len(nums)+1;i++{
-        if i==0{
-            continue
-        }
-        for j:=0;j<(target+sum)/2+1;j++{
-            if nums[i-1]<=j{//如果背包装的下
-                dp[i][j]=dp[i-1][j]+dp[i-1][j-nums[i-1]]
-            }else{
-                dp[i][j]=dp[i-1][j]
-            }
-        }
-    }
-    return dp[len(nums)][(target+sum)/2]
+func abs(x int) int {
+	return int(math.Abs(float64(x)))
 }
 ```
 
-
-
 Javascript：
 ```javascript
 const findTargetSumWays = (nums, target) => {