全排列问题（JAVA和Python实现）

import java.util.Set;
import java.util.TreeSet;

public class Main {
    static Set<String> result=new TreeSet<String>();//用来去掉重复的元素
    public static void fullPermutation(char[] data, int flag){
        if(flag==data.length-1){
            result.add(String.valueOf(data));
        }
        for(int i=flag;i<data.length;i++){
            char temp=data[flag];data[flag]=data[i];data[i]=temp;
            fullPermutation(data,flag+1);
            temp=data[flag];data[flag]=data[i];data[i]=temp;//回溯            
        }
    }
    public static void main(String[] args) {
        char[] data="ABCCDE".toCharArray();
        fullPermutation(data,0);
        for(String x: result)
            System.out.println(x);
    }
}

import itertools
result=set()
data=list(‘ABCCD‘)
for x in itertools.permutations(data,len(data)):
    result.add(x)
for x in sorted(result):
    print ‘‘.join(x)