LeetCode 110 Balanced Binary Tree 平衡二叉树

解法一：

class Solution {
public:
    bool isBalanced(TreeNode* root) {
        return balanceHeight(root)>=0;
    }
    
    int balanceHeight(TreeNode* root)
    {
        if(root==nullptr)
            return 0;
        int left=balanceHeight(root->left);
        int right=balanceHeight(root->right);
        
        if(left<0 || right<0 ||abs(left-right)>1)
            return -1;
        return max(left,right)+1;
    }
};

解法二：

class Solution {
public:
    int height(TreeNode *root) {
            if(root == NULL)return 0;
            return max(height(root->left), height(root->right)) + 1;
        }
        bool isBalanced(TreeNode* root) {
            if(root == NULL)return true;
            return isBalanced(root->left) && isBalanced(root->right) && abs(height(root->left) - height(root->right)) <= 1;

    }
};