Balanced Binary Tree

【题目描述】

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.

【思路】

我是用回归做的，分别得到左右子树的高度，比较是否差值在1之内就可以了。要注意的一点是要比较每个点的子树是否满足条件。

【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 leftheight=treeheight(root->left);        int rightheight=treeheight(root->right);        if(isBalanced(root->left)&&isBalanced(root->right)){            if(abs(leftheight-rightheight)<=1) return true;          else return false;        }        return false;    }    int treeheight(TreeNode* root){        if(root==NULL)  return 0;        return max(treeheight(root->left),treeheight(root->right))+1;    }};