110. Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

檢查這個一顆二元樹是不是高度平衡(這邊的定義為左右兩邊的子樹高度不可以相差大於1)

解法

看code就清楚了

/**
 * 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) 
        {  
            return maxDepth(root) != -1;
        }  
          
        int maxDepth(TreeNode* node)
        {  
            if(!node) 
            {
                return 0;
            }
            
            auto ldepth = maxDepth(node->left);
            auto rdepth = maxDepth(node->right);
            
            if(ldepth == -1 || rdepth == -1 || abs(ldepth - rdepth) > 1)
            {
                return -1;
            }
            
            return max(ldepth, rdepth) + 1;  
        }  
    };