java-生成1~n的序列

Posted 2020-10-09 NEU-2015

import java.util.Scanner;

/**
 * 生成1~n的排列
 * @author NEU-2015
 * 
 */
public class Demo {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int n;
        int[] array;
        while (input.hasNext()) {
            n = input.nextInt();
            array = new int[n];
            print_permutation(n, array, 0);
        }
        input.close();
    }

    private static void print_permutation(int n, int[] array, int i) {
        if (i == n) {    //递归边界
            for (int j = 0; j < array.length; j++) {
                System.out.print(array[j] + " ");
            }
            System.out.println();
        } else {
            for (int k = 1; k <= n; k++) {    //尝试在array[i]中填入各种整数i
                boolean flag = true;
                for (int m = 0; m < i; m++) {
                    if (array[m] == k) {    //如果i已经在array[0]~array[i-1]出现过 则不能再选
                        flag = false;
                    }
                }
                if (flag) {
                    array[i] = k;
                    print_permutation(n, array, i + 1);
                }
            }
        }
    }
}