Subarray Sum Equals K (LC-0560)

class Solution:
    def subarraySum(self, nums, k) -> int:
        rec = {0: [-1]}
        csum = 0
        count = 0
        for ix, n in enumerate(nums):
            csum = csum + n
            if csum - k in rec:
                count = count + len(rec[csum - k])
            if csum not in rec:
                rec[csum] = [ix]
                continue
            rec[csum].append(ix)
        return count