Subarray Sum Equals K

 Given an array of integers and an integer k, find the total number of continuous subarrays whose sum equals to

k.

Example 1:

Input:nums = [1,1,1], k = 2 Output: 2

Note that empty array is not considered as a subarray.

public class CountSubarraySumEqualsK {

    public static void main(String[] args) {

        int arr[] = {3,9,-2,4,1,-7,2,6,-5,8,-3,-7,6,2,1};

        //int arr[] = {1,1,2};

        Map<Integer,Integer> map= new HashMap<>();

        int sum = 0;

        int count = 0;

        int k = 5;

       // int k =2;

        for(int i = 0;i<arr.length;i++){

            sum+=arr[i];

            if(sum==k){

                count++;

            }

            int diff = sum-k;

            if(map.containsKey(diff)){

                count = count + map.get(diff);

            }

            if(map.containsKey(sum)){

                map.put(sum,map.get(sum)+1);

            }else{

                map.put(sum,1);

            }

        }

        System.out.println(count);

    }

}

Result: 7