110. 平衡二叉树

/**
 * 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:
    bool isBalanced(TreeNode* root) 
    {
        if(!root) return true;
        int left = Depth(root->left);
        int right = Depth(root->right);
        int ans = abs(left - right);
        if(ans > 1) return false;
        return isBalanced(root->left) && isBalanced(root->right);
    }
    int Depth(TreeNode* root)
    {
        if(!root) return 0;
        return max(Depth(root->left),Depth(root->right)) + 1;
    }
};