[算法]計算全排列組合數

求一個字符串的全排列所有情況。

輸入：

2

輸出：

012
021
102
120
201
210
6

代碼實現：

package com.darrenchan;

import java.util.*;

public class Yongyou {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        String[] array = new String[n + 1];
        for (int i = 0; i <= n; i++) {
            array[i] = i + "";
        }
        List<String> list = new ArrayList<>();
        listAll(Arrays.asList(array), "", array.length, list);
        for (String s : list) {
            System.out.println(s);
        }
        System.out.println(list.size());
    }

    public static void listAll(List candidate, String prefix, int n, List<String> list){
        if (prefix.length() == n) {
            list.add(prefix);
        }
        for (int i = 0; i < candidate.size(); i++) {
            List tmp = new LinkedList(candidate);
            listAll(tmp, prefix + tmp.remove(i), n, list);//函數中的參數從右邊開始解析
        }
    }
}