添加（0257.二叉树的所有路径.md）：增加typescript版本

problems/0257.二叉树的所有路径.md

@@ -581,7 +581,62 @@ var binaryTreePaths = function(root) {
 };  
 ```
 
+TypeScript：
+
+> 递归法
+
+```typescript
+function binaryTreePaths(root: TreeNode | null): string[] {
+    function recur(node: TreeNode, route: string, resArr: string[]): void {
+        route += String(node.val);
+        if (node.left === null && node.right === null) {
+            resArr.push(route);
+            return;
+        }
+        if (node.left !== null) recur(node.left, route + '->', resArr);
+        if (node.right !== null) recur(node.right, route + '->', resArr);
+    }
+    const resArr: string[] = [];
+    if (root === null) return resArr;
+    recur(root, '', resArr);
+    return resArr;
+};
+```
+
+> 迭代法
+
+```typescript
+// 迭代法2
+function binaryTreePaths(root: TreeNode | null): string[] {
+    let helperStack: TreeNode[] = [];
+    let tempNode: TreeNode;
+    let routeArr: string[] = [];
+    let resArr: string[] = [];
+    if (root !== null) {
+        helperStack.push(root);
+        routeArr.push(String(root.val));
+    };
+    while (helperStack.length > 0) {
+        tempNode = helperStack.pop()!;
+        let route: string = routeArr.pop()!; // tempNode 对应的路径
+        if (tempNode.left === null && tempNode.right === null) {
+            resArr.push(route);
+        }
+        if (tempNode.right !== null) {
+            helperStack.push(tempNode.right);
+            routeArr.push(route + '->' + tempNode.right.val);   // tempNode.right 对应的路径
+        }
+        if (tempNode.left !== null) {
+            helperStack.push(tempNode.left);
+            routeArr.push(route + '->' + tempNode.left.val);    // tempNode.left 对应的路径
+        }
+    }
+    return resArr;
+};
+```
+
 Swift:
+
 > 递归/回溯
 ```swift
 func binaryTreePaths(_ root: TreeNode?) -> [String] {