523. Continuous Subarray Sum

Medium

---

Given an integer array nums and an integer k, return true if nums has a continuous subarray of size at least two whose elements sum up to a multiple of k, or false otherwise.

An integer x is a multiple of k if there exists an integer n such that x = n * k. 0 is always a multiple of k.

Example 1:

Input: nums = [23,2,4,6,7], k = 6
Output:
 true
Explanation:
 [2, 4] is a continuous subarray of size 2 whose elements sum up to 6.

Example 2:

Input: nums = [23,2,6,4,7], k = 6
Output:
 true
Explanation:
 [23, 2, 6, 4, 7] is an continuous subarray of size 5 whose elements sum up to 42.
42 is a multiple of 6 because 42 = 7 * 6 and 7 is an integer.

Example 3:

Input: nums = [23,2,6,4,7], k = 13
Output:
 false

Constraints:

• 1 <= nums.length <= 105

• 0 <= nums[i] <= 109

• 0 <= sum(nums[i]) <= 231 - 1

• 1 <= k <= 231 - 1

class Solution:
    def checkSubarraySum(self, nums: List[int], k: int) -> bool:
        d = {0:0}
        s = 0
        for index, num in enumerate(nums):
            s += num
            if s % k not in d:
                d[s%k] = index+1
            elif d[s%k] < index:
                return True
        return False