Write a function named sortThree that accepts a reference to a vector of integers, all elements of which are guaranteed to be either 0, 1, or 2, and rearranges the values to be in sorted order.
For example, if a vector a contains {2, 0, 2, 1, 1, 0, 0, 2}, the call of sortThree should change its contents to {0, 0, 0, 1, 1, 2, 2, 2}.
This problem could be solved easily by calling an existing library sorting function, but the challenge comes from doing it as efficiently as possible.
Can you do it in a single pass over the vector?
You may assume that the vector does not contain any element values other than 0, 1, or 2.
