leetcode-110-balanced binary tree

/**
 * 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 == NULL)
            return true;
        
        int differ = height(root->left) - height(root->right);
        //cout << differ << endl;
        if(differ < -1 || differ > 1)
            return false;
        else
            return isBalanced(root->left) && isBalanced(root->right);
    }
    
    int height(TreeNode* root){
        if(root == NULL)
            return 0;
        
        int dl = height(root->left);
        int dr = height(root->right);
        
        return dl>dr? dl+1:dr+1;
    }
};

遇见二叉树就是递归！！！不要想其他方法了，好好审题，平衡二叉树：“a binary tree in which the depth of the two subtrees of every node never differ by more than 1.” every node！！！！！