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 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:

    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(object):
    def checkSubarraySum(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: bool
        """
        tmp = 0
        sum_idx = {0: -1}
        for i in xrange(len(nums)):
            tmp += nums[i]
            if k != 0:
                tmp %= k
            if tmp in sum_idx:
                if i - sum_idx[tmp] > 1:
                    return True
            else:
                sum_idx[tmp] = i
            
        return False