Subarrays equals K ​
Subarrays equals K — LeetCode
Given an array and an integer k, count the number of contiguous subarrays whose elements sum to exactly k.
Approach ​
Prefix sum + Counting method. Bit complicated.
Go through summing the array. At each point, check what prefix can be removed to get k. Check if that k has occurred in prefixSums, and the count of occurrence. res += count.
Remarks ​
https://youtu.be/fFVZt-6sgyo?si=9hmDzEURjuh4TKHz