Arrays and Hashing Prefix sums
74. Subarray Sum Equals K
You are given an array of integers nums and an integer k. Return the number of subarrays whose elements
add up to exactly k.
A subarray is a contiguous sequence of elements from nums. Two subarrays are different if they start or
end at different positions.
Example 1
Input: nums = [2, -1, 3, 1, -2, 4], k = 3
4Explanation: Four subarrays add up to 3: [3], [-1, 3, 1], [1, -2, 4] and the first five elements
[2, -1, 3, 1, -2].
Example 2
Input: nums = [1, 1, 1, 1], k = 2
3Explanation: Every pair of neighbours adds up to 2, and there are three pairs, at positions 0–1, 1–2 and 2–3.
Example 3
Input: nums = [5, -5, 5], k = 0
2Explanation: [5, -5] and [-5, 5] both add up to 0. A single element is never 0 here, and the whole array adds up
to 5.
Check your understanding
Work out the answer for this input before you write any code.
Constraints
1 ≤ nums.length ≤ 105-109 ≤ nums[i] ≤ 109-109 ≤ k ≤ 109
Clarifying questions
What you would ask an interviewer before writing any code.