523. Continuous Subarray Sum.py

"""
Given a list of non-negative numbers and a target integer k, write a function to check if the array has a continuous subarray of size at least 2 that sums up to a multiple of k, that is, sums up to n*k where n is also an integer.

 

Example 1:

Input: [23, 2, 4, 6, 7],  k=6
Output: True
Explanation: Because [2, 4] is a continuous subarray of size 2 and sums up to 6.
Example 2:

Input: [23, 2, 6, 4, 7],  k=6
Output: True
Explanation: Because [23, 2, 6, 4, 7] is an continuous subarray of size 5 and sums up to 42.
 

Note:

The length of the array won't exceed 10,000.
You may assume the sum of all the numbers is in the range of a signed 32-bit integer.
"""
class Solution:
    def checkSubarraySum(self, nums: List[int], k: int) -> bool:
        hmap,total = {},0
        for i,num in enumerate(nums):
            total = (total + num) % k
            if total == 0 and i > 0: return True # if total % k =0 that means we have a multiple of k present already and check if the array size is greater than or equal to 2.
            if total not in hmap:
                hmap[total] = i
            else:
                if i - hmap[total] >= 2: return True
        return False