剑指offer-题28：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。

实验平台：牛客网

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解决思路：

java:

import java.util.ArrayList;
import java.util.Collections;

public class Solution {
    public ArrayList<String> Permutation(String str) {
        ArrayList<String> strList = new ArrayList<String>();
        if (str != null && str.trim().length() != 0) {
            char[] strArray = str.toCharArray();
            Permutation(0, strArray, strList);
            Collections.sort(strList);
        }
        return strList;
    }

    public void Permutation(int begin, char[] strArray, ArrayList<String> strList) {
        if (begin == strArray.length) {
            String str = String.valueOf(strArray);
            // System.out.println(str);
            if (!strList.contains(str)) {
                strList.add(str);
            }
        } else {
            for (int i = begin; i < strArray.length; i++) {
                char temp = strArray[i];
                strArray[i] = strArray[begin];
                strArray[begin] = temp;

                Permutation(begin + 1, strArray, strList);

                temp = strArray[i];
                strArray[i] = strArray[begin];
                strArray[begin] = temp;
            }
        }
    }
}

python:

# -*- coding:utf-8 -*-
class Solution:
    def Permutation(self, ss):
        # write code here
        str_list = []
        if ss is not None and len(ss) != 0:
            self.get_list(0, list(ss), str_list)
            str_list.sort()  # 这里用sort()而不用sorted()可以避免不必要的内存开销
        return str_list

    def get_list(self, begin, str_array, str_list):
        if begin == len(str_array):
            str = "".join(str_array)
            if str not in str_list:
                str_list.append(str)
        for i in range(begin, len(str_array)):
            temp = str_array[i]
            str_array[i] = str_array[begin]
            str_array[begin] = temp

            self.get_list(begin+1, str_array, str_list)

            temp = str_array[i]
            str_array[i] = str_array[begin]
            str_array[begin] = temp