Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals to k.
A subarray is a contiguous non-empty sequence of elements within an array.
Example 1:
Input: nums = [1,1,1], k = 2
Output: 2
Example 2:
Input: nums = [1,2,3], k = 3
Output: 2
Constraints:
-
1 <= nums.length <= 2 * 104 -
-1000 <= nums[i] <= 1000 -
-107 <= k <= 107
SOLUTION:
class Solution:
def subarraySum(self, nums: List[int], k: int) -> int:
n = len(nums)
curr = 0
prevsum = {}
ctr = 0
for num in nums:
curr += num
if curr == k:
ctr += 1
if (curr - k) in prevsum:
ctr += prevsum[curr - k]
prevsum[curr] = prevsum.get(curr, 0) + 1
return ctr
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