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:

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

 1 class Solution(object):
 2     def subarraySum(self, nums, k):
 3         """
 4         :type nums: List[int]
 5         :type k: int
 6         :rtype: int
 7         """
 8         sums = {0:1}
 9         s = 0
10         cnt = 0
11         for i in nums:
12             s += i
13             if sums.get(s-k) != None:
14                 cnt += sums[s-k]
15             if sums.get(s) == None:
16                 sums[s] = 1
17             else:
18                 sums[s] += 1
19         return cnt