You are given an array of numbers of length n and a sum s. Create an O(n) algorithm that determines whether there are two numbers in the array that add to the value s. For example, for the array [1,3,2,5] and s = 8, the result is true, but for the same array and s = 10, the result is false. You should clearly describe the algorithm and you should justify why it is O(n). You may write code or pseudo-code. Solutions that are not O(n) are accepted with some penalty.