Balanced Binary Tree

题目：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.

Subscribe to see which companies asked this question

思路：

本题的一个思路就是在当前节点求解左右子树的高度，如果两边高度绝对值相差为1，则返回错误，然后继续判断左右子节点。

本题不难。

代码：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isBalanced(TreeNode* root) {
        if(root==NULL)  return true;
        
        int left=treeDepth(root->left);
        int right=treeDepth(root->right);
        
        if(abs(left-right)>1)   return false;
        
        return isBalanced(root->left)&&isBalanced(root->right);
    }
    
    int treeDepth(TreeNode* root){
        if(root==NULL)  return 0;
        
        int left=1,right=1;
        left+=treeDepth(root->left);
        right+=treeDepth(root->right);
        
        return max(left,right);
    }
};