1
/*
2
Runtime: 21 ms, faster than 98.97% of Java online submissions for Subarray Sum Equals K.
3
Memory Usage: 47.1 MB, less than 85.93% of Java online submissions for Subarray Sum Equals K.
4
*/
5
class Solution {
6
  public int subarraySum(int[] nums, int k) {
7

8
    HashMap<Integer, Integer> map = new HashMap<>();
9
    map.put(0, 1);
10
    int count = 0;
11
    int sum = 0;
12

13
    for (int i = 0; i < nums.length; i++) {
14
      sum += nums[i];
15
      if (map.containsKey(sum - k)) {
16
        count += map.get(sum - k);
17
      }
18
      map.put(sum, map.getOrDefault(sum, 0) + 1);
19
    }
20
    return count;
21
  }
22
}