Subarray Sum Equals K

class Solution:
    def subarraySum(self, nums: List[int], k: int) -> int:
        ht = {0:1}
        res = ps = 0
        for i in nums:
            ps += i
            res += ht.get(ps-k, 0)
            ht[ps] = ht.get(ps, 0) + 1
        return res
#sliding window works for all positives or all negatives