[LeetCode] Balanced Binary Tree 题解_leetcode没有avl树的题目吗?-优快云博客

本文链接：https://blog.youkuaiyun.com/allenzyoung/article/details/50777204

本文介绍了一种通过递归计算树深来判断二叉树是否为平衡树的方法，并提供了清晰的代码实现。

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前言

LeetCode blabla Tree系列稍微不太水的一道题，很有使用价值（可以牵扯到AVL树的概念什么的）。递归仍然是不二选择。

题目

https://leetcode.com/problems/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.
判断一棵二叉树是不是平衡树，这里的标准是每个节点的两个子树深度都不会相差超过1。

分析

写一个辅助函数用于计算树深Depth即可，具体见代码，写的很清晰。

代码

class Solution {
public:
    int Depth(TreeNode* root) {
        if (root == NULL) return 0;
        int LeftD = Depth(root->left);
        int RightD = Depth(root->right);
        return (LeftD+1) > (RightD+1) ? (LeftD+1) : (RightD+1);
    }
  bool isBalanced(TreeNode* root) {
    if (root == NULL) return 1;
    int Left = Depth(root->left);
    int Right = Depth(root->right);
    int diff = Left - Right;
    if (diff > 1 || diff < -1) return 0;
    return isBalanced(root->left) && isBalanced(root->right);
  }
};