Leetcode 560. Subarray Sum Equals K

class Solution:
    def subarraySum(self, nums: List[int], k: int) -> int:
        n = len(nums)
        total = 0
        count  = 0
        stat = collections.defaultdict(int)
        stat[0] = 1
        for i in range(n):
            total += nums[i]
            count += stat[total - k]
            stat[total] += 1
        return count