平衡二叉树

 1int depth(TreeNode* curr, bool& res)
 2{
 3    if(curr == nullptr) return 0;
 4
 5    int left = depth(curr->left, res);
 6    int right = depth(curr->right, res);
 7
 8    if(!res) return 0;
 9
10    if(std::abs(left - right) > 1)
11        res = false;
12
13    return std::max(left, right) + 1;
14}
15bool isBalanced(TreeNode* root)
16{
17    bool res = true;
18    depth(root, res);
19    return res;
20}