leetcode 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.

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不明白这个题为什么自己还是想了很久。

改了很多，有的时候思路不明白还是写下来可以帮助自己理清头绪。

就是求左子树的高度，右子树的高度，假如左子树减右子树的高度的绝对值大于2就不是平衡二叉树了，如果顶点满足要求，就要看左子树是否满足要求，然后右子树。

不知道为什么写错了函数，写了一个专门求左子树高度的函数，专门求右子树的函数，脑子一定是被门夹了。

#include<math.h>
/**
 * 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:
    int maxDepth(TreeNode* root) {
        int lengthleft=0,lengthright=0;
        if (root==NULL) return 0;
        if (root->left == NULL && root->right == NULL){
            return 1;
        }

        if(root->left!=NULL){ 
            lengthleft=maxDepth(root->left)+1;

        }
        if(root->right!=NULL){
            lengthright=maxDepth(root->right)+1;
        }
            
        return lengthright>lengthleft?lengthright:lengthleft;
            
        }
    
    bool isBalanced(TreeNode* root) {
        if(root==NULL) return true;
        int m=maxDepth(root->left)-maxDepth(root->right);
        cout<<m<<endl;
        if(abs(m)<2) return isBalanced(root->left)&&isBalanced(root->right);
        else return false;
    }
    
};