java-生成1~n的序列

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);
                }
            }
        }
    }
}

 2.生成可重集的排列

　　

import java.util.Arrays;
import java.util.Scanner;

/** 
* 生成可重集的排列
* @author NEU-2015 
**/

public class Demo {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int[] array;
        int[] result;
        int n;
        while (input.hasNext()) {
            n = input.nextInt();
            array = new int[n];
            result = new int[n];
            for (int i = 0; i < n; i++) {
                array[i] = input.nextInt();
            }
            Arrays.sort(array);
            print_permutation(n, array, result, 0);
        }
        input.close();
    }

    private static void print_permutation(int n, int[] array, int[] result,
            int cur) {
        if (n == cur) {
            for (int i = 0; i < n; i++) {
                if (i == 0) {
                    System.out.print(result[i]);
                } else {
                    System.out.print("  " + result[i]);
                }
            }
            System.out.println();
        } else {
            for (int k = 0; k < n; k++) {
                int array_charAt_cur_count = 0;
                int result_charAt_cur_count = 0;
                if (k == 0 || array[k] != array[k - 1]) {
                    for (int m = 0; m < n; m++) {
                        if (array[m] == array[k]) {
                            array_charAt_cur_count++;
                        }
                    }
                    for (int m = 0; m < cur; m++) {
                        if (result[m] == array[k]) {
                            result_charAt_cur_count++;
                        }
                    }
                    if (result_charAt_cur_count < array_charAt_cur_count) {
                        result[cur] = array[k];
                        print_permutation(n, array, result, cur + 1);
                    }
                }
            }
        }
    }
}