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Thread: Subarray sum and Hashmap

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    Default Subarray sum and Hashmap

    I'm looking for an explanation of an algorithm of a program solving the following problem: Write a Java program to get the index of the first number and the last number of a subarray where the sum of numbers is zero from a given array of integers.

    Here is the code :

    import java.util.*;
    public class Solution {
        public static List<Integer> subarraySum(int[] nums) {
            List<Integer> temp = new ArrayList<>();
            if (nums == null || nums.length == 0) {
                return temp;
            }
            int pre_Sum = 0;
            Map<Integer, Integer> map = new HashMap<>();
            map.put(pre_Sum, -1);
            for (int i = 0; i < nums.length; i++) {
                pre_Sum += nums[i];
                if (map.containsKey(pre_Sum)) {
                    temp.add(map.get(pre_Sum) + 1);
                    temp.add(i);
                    return temp;
                }
                map.put(pre_Sum, i);
            }
            return temp;
        }
     
    public static void main(String[] args) {
    		int [] nums = {1, 2, 3, -6, 5, 4};
    		System.out.println("Original Array : "+Arrays.toString(nums));
    		System.out.println("Index of the subarray of the said array where the sum of numbers is zero: "+subarraySum(nums));
    	}		
    }

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    Super Moderator Norm's Avatar
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    Default Re: Subarray sum and Hashmap

    I'm looking for an explanation of an algorithm
    Can you post the algorithm that you are asking about?

    To see what the code does, add some print statement that print out the values of variables as the executes. For example print out map and pre_Sum
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Subarray sum and Hashmap

    Sorry, I meant an explanation of this program. Also, I have another question, how useful is Hashmap in that kind of problem like this one.

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    Super Moderator Norm's Avatar
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    Default Re: Subarray sum and Hashmap

    To see what the code does, add some print statements that print out the values of variables as the executes. For example print out map and pre_Sum.
    If you don't understand my answer, don't ignore it, ask a question.

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