110. 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 ofevery node never differ by more than 1.

思路详解：

设置一个高度h与平衡因子balance，如果平衡，则为1，如果不平衡，则为0.如果节点为空，则为h=0,balance = 1;如果节点无孩子 ,h=1,balance = 1;

再向上比较balance即可。

答案详解：

/**

 * 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:
    void judge(TreeNode* root, int &balance,int &h)
    {
         int br,bl,hr,hl;
        if(root==NULL)
        {
            balance=1;
            h=0;
        }
        else if(root->left==NULL&&root->right==NULL)
        {
            balance=1;
            h=1;
        }
        else
        {
            judge(root->left,bl,hl);
            judge(root->right,br,hr);
            h=(hr > hl ? hr : hl)+1;
            if(abs(hr-hl)<2)
                balance=bl&br;
            else
                balance=0;
        }
}

    bool isBalanced(TreeNode* root) {
        int balance,h;
        judge(root,balance,h);
        return balance;
    }
};