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HashMaps and HashSets are useful in a wide variety of challenges. Below is another practice challenge.
Given a list of numbers, can you find all the pairs of numbers whose sum equals k?
The provided boilerplate takes 2 parameters: an array
ar, and the special number
k. This is the raw input format:
The first line of input will contain t. t test cases follow, with each case consisting of n, followed by a line with n numbers. The first number on that line is k, and the remaining numbers are the list.