combination code output needs explanation

[adri00713]

import java.util.ArrayList;
    import java.util.List;
public class CombinationApp {
 
        private static int[] numbers= {1,2,3,4,5,6,7,8,9,10};
        private static int[] sumsum= new int[numbers.length];
 
        private static int sum= 10;
 
        private static void solution(List<Integer> solution) {
 
            System.out.println(solution);
        }
 
        private static void solve(int[] numbers, int i, int sum, List<Integer> solution) {
 
            if (sum == 0) 
                solution(solution);
            else
                for (; i < numbers.length && sumsum[i] >= sum; i++) {
                    if (numbers[i] <= sum) {
                        solution.add(0, numbers[i]);
                        solve(numbers, i+1, sum-numbers[i], solution);
                        solution.remove(0);
                    }
                }
        }
 
        public static void main(String[] args) {
 
            for (int s= 0, i= numbers.length; --i >= 0; ) {
                sumsum[i]= numbers[i]+s;
                s+= numbers[i];
            }
            solve(numbers, 0, sum, new ArrayList<Integer>());
        }
    }
 
 

why is it that this is the output ?
[4, 3, 2, 1]
[7, 2, 1]
[6, 3, 1]
[5, 4, 1]
[9, 1]
[5, 3, 2]
[8, 2]
[7, 3]
[6, 4]
[10]

[Rabbit]

Because that combination of values adds up to the target number, in this case 10. Since it's a recursive function, it repeatedly calls itself to add every combination of numbers in the array until it hits the target value or runs out of numbers to add.

[r035198x]

It's a normal depth first algorithm so maybe revise that algorithm and have a look at the code again.
Here is a variation without the main method setup

    public static void main(String[] args) {
        int[] numberlist = {1,2,3,4,5,6,7,8,9,10};
        Set<String> answersList = new HashSet<String>();
        findSums(numberlist, 0, 0, 10, "", answersList);
        System.out.println(answersList);
 
    }
 
    public static void findSums(int[] list, int index, int current, int K, String previousList, Set<String> answers) {
        if (list.length < index || current > K)
            return;
        for (int i = index; i < list.length; i++) {
            if (current + list[i] == K) {
                answers.add(previousList + " " + list[i]);
            } else if (current + list[i] < K) {
                findSums(list, i + 1, current + list[i], K, previousList + " " + list[i], answers);
            }
        }
    }