Solution: Find Two Numbers That Add up to k—Hashing

Statement

Given an array of integers nums and an integer target, k, find two numbers in the array that sum up to the target k.

There is exactly one solution for each input, and each element of the array can only be used once in the solution. The order of the returned elements does not matter.

Constraints:

• $2 \leq$ nums.length $\leq10^3$ ...