560. Subarray Sum Equals K

https://leetcode.com/problems/subarray-sum-equals-k/

Python

from collections import defaultdict


class Solution:
    def subarraySum(self, nums: List[int], k: int) -> int:
        # Key as the total, value is the count of this total
        sum_map = defaultdict(lambda: 0)

        # counter to accumulate the answer
        count = 0

        # The current sum
        total = 0

        # Edge case, total == 0 initial with one possible combination: []
        sum_map[0] = 1

        for num in nums:
            total += num
            count += sum_map[total-k]
            sum_map[total] += 1

        return count