二叉树的深度

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败给你的黑色幽默丶

最新推荐文章于 2025-08-02 12:01:09 发布

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分类专栏： leetcode 文章标签： java

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剑指 Offer 55 - I. 二叉树的深度
https://leetcode-cn.com/problems/er-cha-shu-de-shen-du-lcof/

BFS-层序

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int maxDepth(TreeNode root) {
        if(root == null) return 0;

        Queue<TreeNode> que = new LinkedList<>();
        que.offer(root);
        int height = 1;
        int levelSize = 1;
        
        while(que.size() != 0){
            TreeNode node = que.poll();
            levelSize--;

            if(node.left != null) que.offer(node.left);
            if(node.right != null) que.offer(node.right);
            if(que.size() != 0 && levelSize == 0){
                height++;
                levelSize = que.size();
            }
    }
        return height;
}
}

递归 DFS-后序

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int maxDepth(TreeNode root) {
        if(root == null) return 0;

        return Math.max(maxDepth(root.left),maxDepth(root.right)) + 1;
    }
}