560. Subarray Sum Equals K

Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k.

Example 1:

Input:nums = [1,1,1], k = 2
Output: 2

Note:

1. The length of the array is in range [1, 20,000].
2. The range of numbers in the array is [-1000, 1000] and the range of the integer k is [-1e7, 1e7].

 class Solution(object):
     def subarraySum(self, nums, k):
         """
         :type nums: List[int]
         :type k: int
         :rtype: int
         """
         sums = {0:1}
         s = 0
         cnt = 0
         for i in nums:
             s += i
             if sums.get(s-k) != None:
                 cnt += sums[s-k]
             if sums.get(s) == None:
                 sums[s] = 1
             else:
                 sums[s] += 1
         return cnt