JZ27 字符串的排列

题目描述

输入一个字符串,按字典序打印出该字符串中字符的所有排列。例如输入字符串abc,则按字典序打印出由字符a,b,c所能排列出来的所有字符串abc,acb,bac,bca,cab和cba。

输入描述:

输入一个字符串,长度不超过9(可能有字符重复),字符只包括大小写字母。

import java.util.*;
public class Solution {
    public ArrayList<String> Permutation(String str) {
        ArrayList<String> arrayList = new ArrayList();
        char[] chars = str.toCharArray();
        getPermutation(chars,0,arrayList);
        Collections.sort(arrayList);
        return arrayList;
    }

    private void getPermutation(char[] chars, int index,ArrayList<String> arrayList) {
        if (index == chars.length-1 && !arrayList.contains(new String(chars))) {

            arrayList.add(new String(chars));
            return;
        }
        for (int i = index; i < chars.length; i++) {
            swap(chars,index,i);
            getPermutation(chars,index+1,arrayList);
            swap(chars,index,i);
        }
    }

    private void swap(char[] chars,int index, int i) {
        char temp = chars[i];
        chars[i] = chars[index];
        chars[index] = temp;
    }
}