《剑指offer—面试题38：字符串的排序》

《剑指offer—面试题38：字符串的排序》
注明：仅个人学习笔记

https://www.nowcoder.com/profile/631996/codeBookDetail?submissionId=1512262
https://www.cnblogs.com/liang1101/p/6376210.html

import java.util.ArrayList;
import java.util.Iterator;
import java.util.TreeSet;

/**
*
*
* 字符串的排列 输入一个字符串，打印出该字符串的所有排列 例如输入abc，打印出来，abc,acb,bac,bca,cba,cab
*
*/
public class StringRank38
{
public ArrayList Permutation(String str)
{
ArrayList result = new ArrayList();

    if (str == null || str.length() == 0)
    {
        return result;
    }

    char[] chars = str.toCharArray();

    TreeSet<String> temp = new TreeSet<String>();// 用该容器，避免重复数据

    Permutation(chars, 0, temp);
    result.addAll(temp);

    return result;

}

public void Permutation(char[] chars, int begin, TreeSet<String> result)
{

    if (chars == null || chars.length == 0 || begin < 0 || begin > chars.length - 1)
    {
        return;
    }

    if (begin == chars.length - 1)
    {
        result.add(String.valueOf(chars));
    } else
    {
        for (int i = begin; i < chars.length; i++)
        {
            swap(chars, begin, i);

            Permutation(chars, begin + 1, result);

            swap(chars, begin, i);// 还原当前chars
        }
    }

}

private void swap(char[] x, int a, int b)
{
    // TODO Auto-generated method stub

    char t = x[a];
    x[a] = x[b];
    x[b] = t;

}

public static void main(String[] args)
{
    String str = "abc";

    StringRank38 sk = new StringRank38();
    ArrayList<String> list = sk.Permutation(str);

    Iterator<String> iter = list.iterator();

    for (; iter.hasNext();)
    {
        System.out.println(iter.next());
    }
}

}