0110 | 平衡二叉树.md

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

/**
 * 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:
    int height(TreeNode *root)
    {
        if(!root)
            return 0;
        int heightleft = height(root->left);
        int heightright = height(root->right);
        if(heightleft == -1 || heightright == -1 || abs(heightleft-heightright) > 1)
        {
            return -1;
        }
        else
        {
            return max(heightleft, heightright) + 1;
        }
    }
    bool isBalanced(TreeNode* root) {
        return height(root) >= 0;
    }
};