Merge pull request #1462 from xiaofei-2020/exTree02

添加（1382.将二叉搜索树变平衡.md）：增加typescript版本

problems/1382.将二叉搜索树变平衡.md

@@ -188,6 +188,30 @@ var balanceBST = function(root) {
 };
 ```
 
+TypeScript：
+
+```typescript
+function balanceBST(root: TreeNode | null): TreeNode | null {
+    const inorderArr: number[] = [];
+    inorderTraverse(root, inorderArr);
+    return buildTree(inorderArr, 0, inorderArr.length - 1);
+};
+function inorderTraverse(node: TreeNode | null, arr: number[]): void {
+    if (node === null) return;
+    inorderTraverse(node.left, arr);
+    arr.push(node.val);
+    inorderTraverse(node.right, arr);
+}
+function buildTree(arr: number[], left: number, right: number): TreeNode | null {
+    if (left > right) return null;
+    const mid = (left + right) >> 1;
+    const resNode: TreeNode = new TreeNode(arr[mid]);
+    resNode.left = buildTree(arr, left, mid - 1);
+    resNode.right = buildTree(arr, mid + 1, right);
+    return resNode;
+}
+```
+
 
 
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