Zero Sum Subarrays

PrefixSum.java

//geeksforgeeks.org/find-if-there-is-a-subarray-with-0-sum/

import java.util.ArrayList;

public class PrefixSum {

    public static int[] recoverOriginalArray(int[] array) {
        int l = array.length;
        int[] result = new int[l];
        result[0] = array[0];
        for(int i = 1; i < l; i++) {
            result[i] = array[i] - array[i - 1];
        }
        return result;
    }

    public static int[] prefixSum(int[] array) {
        int l = array.length;
        int[] result = new int[l];
        result[0] = array[0];
        for(int i = 1; i < l; i++) {
           result[i] = result[i - 1] + array[i]; 
        }
        return result;
    }

    //Subarray's with 0 sum
    public static ArrayList<int[]> countZeroSumSubArrays(int[] array) {
        int l = array.length;
        int sum = 0;
        ArrayList<int[]> result = new ArrayList<>(); 
        for(int i = 0; i < l; i++) {
            for(int j = i; j < l; j++) {
               sum += array[j];
               if(sum == 0) {
                   result.add(new int[] {i, j});
               }  
            }
            sum = 0;
        }
        return result;
    }

    public static void main(String[] args) {
        System.out.println("Beginning of the program");
        int[] a = prefixSum(new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 0});
        for(int i = 0; i < a.length; i++) {
            System.out.print(a[i] + " ");
        }
        System.out.println();


        int[] recovered = recoverOriginalArray(a);
        for(int i = 0; i < recovered.length; i++) {
            System.out.print(recovered[i] + " ");
        } 
        System.out.println();

        ArrayList<int[]> result = countZeroSumSubArrays(new int[] {3, 2, -1, 1, 1, -1, 2, 3, -3, 6, 2, -8, 10});
        System.out.println("The following " + result.size() + " results were found"); 
        for(int[] r: result) {
            System.out.println(r[0] + ", " + r[1]);
        }
        
    }
}

$ java PrefixSum
Beginning of the program
1 3 6 10 15 21 28 36 45 45
1 2 3 4 5 6 7 8 9 0
The following 6 results were found
2, 3
2, 5
4, 5
7, 8
7, 11
9, 11