Given an array of integers [20, 10, 5, 50, 0], find all unique pairs of numbers that sum to a target value (e.g., 9). Print each pair without duplicates.

A simple and efficient way to find all unique pairs that sum to a target is to use a hash set. Iterate over the array, and for each element x compute its complement y = target - x. If y is already in the set, you have found a pair (x, y). Store the pair in a result list, ensuring you only add each unordered pair once (e.g., by always storing the smaller element first). After processing the element, add it to the set. This algorithm runs in O(n) time and O(n) space. For the example array [20, 10, 5, 50, 0] and target 9, the algorithm will find no pairs because no two numbers add up to 9. If the target were 15, the algorithm would return the pair (10, 5). This approach is straightforward, handles duplicates correctly, and scales well for large inputs.