ContinuousSubArraySum.py

# Given an integer array nums and an integer k, return true if nums has a good subarray or false otherwise.

# A good subarray is a subarray where:

# its length is at least two, and
# the sum of the elements of the subarray is a multiple of k.
# Note that:

# A subarray is a contiguous part of the array.
# 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

class Solution:
    def checkSubarraySum(self, nums: List[int], k: int) -> bool:
        HashMap = {0:-1}
        total  = 0
        for i, val in enumerate(nums):
            total += val
            r = total % k
            if r not in HashMap:
                HashMap[r] = i

            elif r in HashMap and i - HashMap[r] > 1:
                return True

        return False
    
# Runtime 983 ms Beats 61.3%
# Memory 36.2 MB Beats 26.92%