Balanced Binary Tree

class Solution {

public:

bool isBalanced(TreeNode* root) {

if(!root)

return true;

return depth(root)>0;

}

int depth(TreeNode* root){

if(!root)

return 0;

int l=depth(root->left), r=depth(root->right);

if(l<0||r<0||abs(l-r)>1) return -1;//剪枝 every node!!!!!!!!!!!!!!!!!!!!!!!!!!!!

return 1+max(l,r);

}

};