unique feature without advanced features

I want an algorithm that generates the function [a,b,c}=unique(Y) although there are forums what I need is for it to be only with structural control sequences if else for while etc but not advanced functions of either Matlab or from mathcad since when you want to replicate the function elsewhere it is complicated, it would be appreciated if you have a way to do it 

 

What would the mathcad programming of this algorithm be like as it is in the image so it is easier to carry out the function?