38.二叉树的深度

题目描述

输入一棵二叉树,求该树的深度。从根结点到叶结点依次经过的结点(含根、叶结点)形成树的一条路径,最长路径的长度为树的深度。

题目解答

方法一:递归

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public int TreeDepth(TreeNode root) {
        if(root==null){
            return 0;
        }
        int left=TreeDepth(root.left);
        int right=TreeDepth(root.right);
        return Math.max(left,right)+1;
    }
}

方法二:层次遍历

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
import java.util.Queue;
import java.util.LinkedList;

public class Solution {
    public int TreeDepth(TreeNode root) {
        if(root==null){
            return 0;
        }
        
        Queue<TreeNode> queue=new LinkedList<>();
        queue.add(root);
        int depth=0,count=0,nextCount=1;
        while(queue.size()!=0){
            TreeNode top=queue.poll();
            count++;
            if(top.left!=null){
                queue.add(top.left);
            }
            if(top.right!=null){
                queue.add(top.right);
            }
            if(count==nextCount){
                nextCount=queue.size();
                count=0;
                depth++;
            }
        }
        return depth;
    }
}

 

posted @ 2019-01-08 21:12  chan_ai_chao  阅读(121)  评论(0编辑  收藏  举报