[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.

思考：求二叉树高的变形，加上判断即可。

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
private:
    bool flag;
public:
    int DFS(TreeNode *root)
    {
        if(root)
        {
            int height1=DFS(root->left);
            int height2=DFS(root->right);
            if(abs(height1-height2)>1) flag=false;
            return max(height1,height2)+1;
        }
        else return 0;
    }
    bool isBalanced(TreeNode *root) {
        flag=true;
        int height=DFS(root);//树高
        return flag;
    }
};