523. Continuous Subarray Sum

https://leetcode.com/problems/continuous-subarray-sum/

Python

class Solution:
    def checkSubarraySum(self, nums: List[int], k: int) -> bool:
        if k <= 0:
            return

        # key: sum mod k, value: index
        prefix_map = {0: -1}
        remainder = 0

        for i, num in enumerate(nums):
            remainder += num
            remainder %= k

            if remainder in prefix_map:
                if i - prefix_map.get(remainder) > 1:
                    return True
            else:
                prefix_map[remainder] = i

        return False