523. Continuous Subarray Sum

Posted 2020-10-14 Learning is fun.

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 the 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:

1. The length of the array won‘t exceed 10,000.
2. You may assume the sum of all the numbers is in the range of a signed 32-bit integer.

 

 1 class Solution(object):
 2     def checkSubarraySum(self, nums, k):
 3         """
 4         :type nums: List[int]
 5         :type k: int
 6         :rtype: bool
 7         """
 8         s = 0
 9         sums = {0: -1}
10         for i, n in enumerate(nums):
11             s += n
12             if k == 0:
13                 t = s
14             else:
15                 t = s % k
16             if t in sums:
17                 if i-sums[t] > 1:
18                     return True
19             else:
20                 sums[t] = i
21         return False