LeetCode-Balanced Binary Tree

最新推荐文章于 2020-06-14 12:37:28 发布

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本文介绍了如何使用栈实现平衡二叉树的高度判断算法，详细解释了算法的时间复杂度和空间复杂度，并提供了Java版本的源码。

题目：https://oj.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.

源码：Java版本
算法分析：使用栈。时间复杂度O(n)，空间复杂度O(logn)

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isBalanced(TreeNode root) {
        return balancedHeight(root)>=0?true:false;
    }
    
    private int balancedHeight(TreeNode root) {
        if(root==null) {
            return 0;
        }
        int left=balancedHeight(root.left);
        int right=balancedHeight(root.right);
        
        if(left<0 || right <0 || Math.abs(left-right)>1) {
            return -1;
        }
        return Math.max(left,right)+1;
    }
}