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) {
int depth = 0;
return IsBalanced(pRoot,depth);
}
bool IsBalanced(TreeNode *root, int & dep){
if(root == NULL){
return true;
}
int left = 0;
int right = 0;
if(IsBalanced(root->left,left) && IsBalanced(root->right, right)){
int dif = left - right;
if(dif<-1 || dif >1)
return false;
dep = (left > right ? left : right) + 1;
return true;
}
return false;
}
};