平衡二叉树

输入一棵二叉树，判断该二叉树是否是平衡二叉树。

class Solution {public:    bool IsBalanced_Solution(TreeNode* pRoot) {        bool res=1;        getHeight(pRoot,res);        return res;    }    int getHeight(TreeNode* root,bool &res){        if(root==NULL)            return 0;        //如果已经判断出不是平衡二叉树了，那就不用再继续再往深里搜索了        if(res==0)            return -1;        else{            int leftHeight=getHeight(root->left,res);            int rightHeight=getHeight(root->right,res);            res=abs(leftHeight-rightHeight)<=1;              return max(leftHeight+1,rightHeight+1);          }    }};