93题 Balanced Binary Tree

最新推荐文章于 2025-12-13 12:19:21 发布

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本文介绍如何使用递归方法判断给定的二叉树是否为高度平衡树，关键在于比较左右子树的最大深度差，并返回结果。通过 helper 函数实现深度计算和不平衡判断。

Balanced Binary Tree

Description
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.

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
class ResultType{
    public boolean isBalanced;
    public int maxDepth ;
    public ResultType(boolean isBalanced , int maxDepth){
        this.isBalanced = isBalanced ;
        this.maxDepth = maxDepth ;

    }
}
public class Solution {
    /**
     * @param root: The root of binary tree.
     * @return: True if this Binary tree is Balanced, or false.
     */

    public boolean isBalanced(TreeNode root) {
        // write your code here
        return helper(root).isBalanced ;
    }
    private ResultType helper(TreeNode root){
        if(root == null ){
            return new ResultType(true , 0) ;
        }
        ResultType left = helper(root.left);
        ResultType right = helper(root.right);
        if(! left.isBalanced || ! right.isBalanced){
            return new ResultType(false , -1) ;
        }
        if(Math.abs(left.maxDepth - right.maxDepth) > 1){
            return new ResultType(false , -1) ;
        }
        return new ResultType(true , Math.max(left.maxDepth, right.maxDepth)+1) ;
    }
}