560 Subarray Sum Equals K

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

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class Solution:
    def subarraySum(self, nums: List[int], k: int) -> int:
        count, s, d = 0, 0, {}
        d[0] = 1
        for num in nums:
            s += num
            if (s - k) in d:
                count += d[s - k]
            d[s] = d.get(s, 0) + 1
        return count