返回字符串数组中 [0, n) 的排列，public static String[] printPermutation(int n)

Question

/* Return permutation of [0, n) in a String array, for example 
           when n=3, it should return:
          012
          021
          102
          120
          201
          210
          the order does not matter
         */

Answer 1

我在this site 找到的一个解决方案：围绕它构建程序并添加您喜欢的数组。

package test;

import java.util.ArrayList;

public class Permutation {

    public static void main(String[] args) {

        for(ArrayList<Integer>  al: permute(new int[]{1,2,3})){
            for(Integer i : al){
                System.out.print( i);
            }
            System.out.println(" ");
        }
    }

        public static ArrayList<ArrayList<Integer>> permute(int[] num) {
            ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
            permute(num, 0, result);
            return result;
        }

        public static void permute(int[] num, int start, ArrayList<ArrayList<Integer>> result) {

            if (start >= num.length) {
                ArrayList<Integer> item = convertArrayToList(num);
                result.add(item);
            }

            for (int j = start; j <= num.length - 1; j++) {
                swap(num, start, j);
                permute(num, start + 1, result);
                swap(num, start, j);
            }
        }

        private static ArrayList<Integer> convertArrayToList(int[] num) {
            ArrayList<Integer> item = new ArrayList<Integer>();
            for (int h = 0; h < num.length; h++) {
                item.add(num[h]);
            }
            return item;
        }

        private static void swap(int[] a, int i, int j) {
            int temp = a[i];
            a[i] = a[j];
            a[j] = temp;
        }


}