添加（0104.二叉树的最大深度.md）：增加typescript版本

problems/0104.二叉树的最大深度.md

@@ -598,7 +598,55 @@ var maxDepth = function(root) {
 };
 ```
 
+## TypeScript：
+
+> 二叉树的最大深度：
+
+```typescript
+// 后续遍历（自下而上）
+function maxDepth(root: TreeNode | null): number {
+    if (root === null) return 0;
+    return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
+};
+
+// 前序遍历(自上而下)
+function maxDepth(root: TreeNode | null): number {
+    function recur(node: TreeNode | null, count: number) {
+        if (node === null) {
+            resMax = resMax > count ? resMax : count;
+            return;
+        }
+        recur(node.left, count + 1);
+        recur(node.right, count + 1);
+    }
+    let resMax: number = 0;
+    let count: number = 0;
+    recur(root, count);
+    return resMax;
+};
+
+// 层序遍历（迭代法）
+function maxDepth(root: TreeNode | null): number {
+    let helperQueue: TreeNode[] = [];
+    let resDepth: number = 0;
+    let tempNode: TreeNode;
+    if (root !== null) helperQueue.push(root);
+    while (helperQueue.length > 0) {
+        resDepth++;
+        for (let i = 0, length = helperQueue.length; i < length; i++) {
+            tempNode = helperQueue.shift()!;
+            if (tempNode.left) helperQueue.push(tempNode.left);
+            if (tempNode.right) helperQueue.push(tempNode.right);
+        }
+    }
+    return resDepth;
+};
+```
+
+
+
 ## C
+
 二叉树最大深度递归
 ```c
 int maxDepth(struct TreeNode* root){