Balanced Binary Tree 判断平衡二叉树

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int depth(TreeNode *node){
        if(node==NULL)
            return 0;
        int i=depth(node->left);
        int j=depth(node->right);
        return max(i,j)+1;
    }
    bool isBalanced(TreeNode *root) {
        if(root==NULL)
            return true;
        int leftDep=depth(root->left);
        int rightDep=depth(root->right);
        if(abs(leftDep-rightDep)<=1)
            return isBalanced(root->left) && isBalanced(root->right);
        else
            return false;
    }
};