Leetcode - Tree - Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    bool isBalanced(TreeNode *root) {        int depth;        return checkBalanced(root, depth);    }    bool checkBalanced(TreeNode *root, int &depth) // 给checkBalanced传入depth是为了求depth的值，由于checkBalanced只能返回一个值，所以传入一个引用，求depth的值。    {        if(root==NULL)        {            depth=0;            return true;        }        int depthLeft,depthRight;        bool leftBalanced=checkBalanced(root->left, depthLeft);        bool rightBalanced=checkBalanced(root->right, depthRight);        depth=max(depthLeft+1,depthRight+1);        return leftBalanced&&rightBalanced&&(abs(depthLeft-depthRight)<=1);    }};