0560 - Subarray Sum Equals K

0560 - Subarray Sum Equals K

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

Examples

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

Input: nums = [1,2,3], k = 3 Output: 2

Constraints

• 1 <= nums.length <= 2 * 104

• -1000 <= nums[i] <= 1000

• 107 <= k <= 1074

Java Solution

class Solution {
    public int subarraySum(int[] nums, int k) {
        int count = 0, sum = 0;
        HashMap <Integer, Integer> map = new HashMap<>();
        map.put(0, 1);
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            if (map.containsKey(sum - k))
                count += map.get(sum - k);
            map.put(sum, map.getOrDefault(sum, 0) + 1);
        }
        return count;
    }
}