Question

How to print all possible ways to write a number (N) as a sum of two or more positive integers in Java

Answer 1

import java.util.ArrayList;
import java.util.List;

public class AllWaysToWriteANumberAsSumOfTwoOrMoreInts_Java {
    public static void printList(List<Integer> list) {
        if (list.size() != 1) {
            for (int i = 0; i < list.size(); i++) {
                if (i < list.size() - 1) {
                    System.out.print(list.get(i) + " + ");
                } else {
                    System.out.print(list.get(i));
                }
            }
        }
        System.out.println();
    }

    public static void allWaysToWriteANumberAsSumOfTwoOrMoreInts(List<Integer> list, int i, int n) {
        if (n == 0) {
            printList(list);
        }

        for (int j = i; j <= n; j++) {
            list.add(j);
            allWaysToWriteANumberAsSumOfTwoOrMoreInts(list, j, n - j);
            list.remove(list.size() - 1);
        }
    }

    public static void main(String[] args) {
        int n = 5; // The number

        List<Integer> list = new ArrayList<>();
        
        allWaysToWriteANumberAsSumOfTwoOrMoreInts(list, 1, n);
    }
}



/*
run:

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

*/

 

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