蓝桥杯 DFS 二叉树最大深度（简单）

浅沫记忆

问题描述

给定一个二叉树，找出其最大深度。
二叉树的深度为根节点到最远叶子节点的最长路径上的节点数。
说明: 叶子节点是指没有子节点的节点。
示例：
给定二叉树 [3,9,20,null,null,15,7]，
3
/ \
9  20
/  \
15   7
返回它的最大深度 3 。
参考代码

import java.util.Stack;
public class Main {
public static void main(String[] args) {
int [][]aa = {
{0,1,1,0,0,0,0},
{1,0,0,0,0,0,0},
{1,0,0,0,0,1,1},
{0,0,0,0,0,0,0},
{0,0,0,0,0,0,0},
{0,0,1,0,0,0,0},
{0,0,1,0,0,0,0},
};
String[]nodes = {"3","9","20","null","null","15","7"};
Stack<Integer>sta = new Stack<Integer>();
boolean [] check = new boolean[nodes.length];
int max = 0;
sta.push(0);
check[0] = true;
while (!sta.isEmpty()) {
int temp = sta.peek();
boolean flag = true;
for (int i = 0; i < check.length; i++) {
if (!check[i]&&aa[temp][i] == 1) {
sta.push(i);
flag = false;
check[i] = true;
break;
}
}
if (flag) {
if (max<sta.size()) {
max = sta.size();
}
sta.pop();
}
}
System.out.println(max);
}
}