Merge pull request youngyangyang04#1074 from xiaofei-2020/tree12

添加（0110.平衡二叉树.md）：增加typescript版本

Author: youngyangyang04

problems/0110.平衡二叉树.md

@@ -627,7 +627,26 @@ var isBalanced = function(root) {
 };
 ```
 
+## TypeScript
+
+```typescript
+// 递归法
+function isBalanced(root: TreeNode | null): boolean {
+    function getDepth(root: TreeNode | null): number {
+        if (root === null) return 0;
+        let leftDepth: number = getDepth(root.left);
+        if (leftDepth === -1) return -1;
+        let rightDepth: number = getDepth(root.right);
+        if (rightDepth === -1) return -1;
+        if (Math.abs(leftDepth - rightDepth) > 1) return -1;
+        return 1 + Math.max(leftDepth, rightDepth);
+    }
+    return getDepth(root) !== -1;
+};
+```
+
 ## C
+
 递归法：
 ```c
 int getDepth(struct TreeNode* node) {