输出集合中所有数据项组合

Problem

Print all combination of a specified list items.

Solution

public class Combination{
    public static void main(String[] arguments){
        int[] list = {1, 2, 3, 4};
        int[] preceding = {};
        Combination.Comb(preceding, list);
    }
    
    private static void Print(int[] list){
        for(int i = 0; i < list.length;  ++i){
            System.out.print(list[i] + " ");
        }
        System.out.println();
    }

    private static void Copy(int[] destination, int[] source, int start){
        for(int i = start; i < source.length; ++i){
            destination[i - start] = source[i];
        }
    }
    
    public static void Comb(int[] preceding, int[] list){
        if(list.length == 0){
            Print(preceding);
        }else{
            int[] newPreceding = new int[preceding.length + 1];
            Copy(newPreceding, preceding, 0);
            newPreceding[preceding.length] = list[0];
            
            int[] newList = new int[list.length - 1];
            Copy(newList, list, 1);
            
            Comb(newPreceding, newList);
            Comb(preceding, newList);
        }
    }  
}

Output

1 2 3 4 
1 2 3 
1 2 4 
1 2 
1 3 4 
1 3 
1 4 
1 
2 3 4 
2 3 
2 4 
2 
3 4 
3 
4