JAVA internship job search-depth first search

Depth-first search, also known as dfs, is a search algorithm. The best practice for this kind of algorithm is topic practice. Here are a few examples to explain dfs

Example 1: Enter n, please output the full arrangement of 1-n

深度优先搜索的思路如下

public static void dfs(int step){
    判断边界，递归的出口

    for(尝试每一种可能){
        继续下一步dfs(step+1)
    }
}

Here suppose n = 3, then it is to solve the whole arrangement of 1-3, because the simple can easily get the answer

123,132,213,231,312,321

Then the idea of ​​using dfs is that the specific code is as follows

public static void dfs(int step){
    if(step == 4){
        打印前三步排好的数字
    }

    从1-3开始看看能不能排
    dfs(step+1)
}

package com.note;

import java.util.Scanner;

/**
 * 输入n
 * 输出1-n的全排列
 */
public class dfs数的全排列 {
    private static int n;
    private static int[] arr;
    private static int[] book;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        arr = new int[n+1];
        book = new int[n+1];

        dfs(1);

    }

    private static void dfs(int step) {
        if (step == n+1){
            for (int i=1;i<=n;i++)
                System.out.print(arr[i]);
            System.out.println();
            return;
        }

        for (int i=1;i<=n;i++){
            if (book[i] == 0){
                book[i] = 1;
                arr[step] =i;
                dfs(step+1);
                book[i] = 0;
            }
        }


    }
}