Merge pull request #1058 from xiaofei-2020/tree2

添加（二叉树的递归遍历.md）：增加typescript版本

problems/二叉树的迭代遍历.md

@@ -454,6 +454,61 @@ var postorderTraversal = function(root, res = []) {
 };
 ```
 
+TypeScript:
+
+```typescript
+// 前序遍历（迭代法）
+function preorderTraversal(root: TreeNode | null): number[] {
+    if (root === null) return [];
+    let res: number[] = [];
+    let helperStack: TreeNode[] = [];
+    let curNode: TreeNode = root;
+    helperStack.push(curNode);
+    while (helperStack.length > 0) {
+        curNode = helperStack.pop()!;
+        res.push(curNode.val);
+        if (curNode.right !== null) helperStack.push(curNode.right);
+        if (curNode.left !== null) helperStack.push(curNode.left);
+    }
+    return res;
+};
+
+// 中序遍历（迭代法）
+function inorderTraversal(root: TreeNode | null): number[] {
+    let helperStack: TreeNode[] = [];
+    let res: number[] = [];
+    if (root === null) return res;
+    let curNode: TreeNode | null = root;
+    while (curNode !== null || helperStack.length > 0) {
+        if (curNode !== null) {
+            helperStack.push(curNode);
+            curNode = curNode.left;
+        } else {
+            curNode = helperStack.pop()!;
+            res.push(curNode.val);
+            curNode = curNode.right;
+        }
+    }
+    return res;
+};
+
+// 后序遍历（迭代法）
+function postorderTraversal(root: TreeNode | null): number[] {
+    let helperStack: TreeNode[] = [];
+    let res: number[] = [];
+    let curNode: TreeNode;
+    if (root === null) return res;
+    helperStack.push(root);
+    while (helperStack.length > 0) {
+        curNode = helperStack.pop()!;
+        res.push(curNode.val);
+        if (curNode.left !== null) helperStack.push(curNode.left);
+        if (curNode.right !== null) helperStack.push(curNode.right);
+    }
+    return res.reverse();
+};
+```
+
 Swift:
 
 > 迭代法前序遍历

problems/二叉树的递归遍历.md

@@ -270,40 +270,6 @@ func postorderTraversal(root *TreeNode) (res []int) {
 }
 ```
 
-javaScript:
-
-```js
-
-前序遍历:
-
-var preorderTraversal = function(root, res = []) {
-    if (!root) return res;
-    res.push(root.val);
-    preorderTraversal(root.left, res)
-    preorderTraversal(root.right, res)
-    return res;
-};
-
-中序遍历:
-
-var inorderTraversal = function(root, res = []) {
-    if (!root) return res;
-    inorderTraversal(root.left, res);
-    res.push(root.val);
-    inorderTraversal(root.right, res);
-    return res;
-};
-
-后序遍历:
-
-var postorderTraversal = function(root, res = []) {
-    if (!root) return res;
-    postorderTraversal(root.left, res);
-    postorderTraversal(root.right, res);
-    res.push(root.val);
-    return res;
-};
-```
 Javascript版本：
 
 前序遍历：
@@ -358,7 +324,51 @@ var postorderTraversal = function(root) {
 };
 ```
 
+TypeScript:
+
+```typescript
+// 前序遍历
+function preorderTraversal(node: TreeNode | null): number[] {
+    function traverse(node: TreeNode | null, res: number[]): void {
+        if (node === null) return;
+        res.push(node.val);
+        traverse(node.left, res);
+        traverse(node.right, res);
+    }
+    const res: number[] = [];
+    traverse(node, res);
+    return res;
+}
+
+// 中序遍历
+function inorderTraversal(node: TreeNode | null): number[] {
+    function traverse(node: TreeNode | null, res: number[]): void {
+        if (node === null) return;
+        traverse(node.left, res);
+        res.push(node.val);
+        traverse(node.right, res);
+    }
+    const res: number[] = [];
+    traverse(node, res);
+    return res;
+}
+
+// 后序遍历
+function postorderTraversal(node: TreeNode | null): number[] {
+    function traverse(node: TreeNode | null, res: number[]): void {
+        if (node === null) return;
+        traverse(node.left, res);
+        traverse(node.right, res);
+        res.push(node.val);
+    }
+    const res: number[] = [];
+    traverse(node, res);
+    return res;
+}
+```
+
 C:
+
 ```c
 //前序遍历：
 void preOrderTraversal(struct TreeNode* root, int* ret, int* returnSize) {