LeetCode 110. Balanced Binary Tree（判断平衡二叉树）

最新推荐文章于 2025-12-09 14:04:42 发布

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原文链接：http://www.cnblogs.com/douzujun/p/10980339.html

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#数据结构与算法

本文探讨了如何确定一个二叉树是否为高度平衡。高度平衡的二叉树定义为：对于每一个节点，其两个子树的深度相差不超过1。通过示例详细解释了判断逻辑，并提供了C++实现代码。

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.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

Return true.

Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

Return false.

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