28 列出数组中数的全部组合

//列出一个数组中数的全部组合。如{1,2}则列出12,21
import java.util.*;
public class ListCombinations1{
    public static void main(String args[]){
        String[] array = {"1","2","3"};
        listCombinations(Arrays.asList(array),"");
    }
    public static void listCombinations(List candidate, String prefix){
        if(candidate.isEmpty()){
            System.out.println(prefix);
        }
        for(int i=0; i<candidate.size(); i++){
            List temp = new LinkedList(candidate);
            listCombinations(temp, prefix+temp.remove(i));
        }
    }
}

    

//列出一个数组中数的全部组合。如{1,2}则列出1,2,12,21
import java.util.*;
public class ListCombinations{
    public static void main(String args[]){
        String[] array = {"1","2","3"};//是String 而非int!!!
        listCombinations(Arrays.asList(array),"");
    }
    public static void listCombinations(List candidate, String prefix){
        System.out.println(prefix);//与上段代码只有此处不同
        for(int i=0; i<candidate.size(); i++){
            List temp = new LinkedList(candidate);
            listCombinations(temp, prefix+temp.remove(i));
        }
    }
}