Just a question in general, (In c) I'm trying to printing the intersection and union of two sets that are containing letters, numbers punctuations and symbols, how do I write an union function to print all the elements but what they in common(only print once), and for the intersection function, only print elements that are in common

(let's say we have setA contains 1,2,3,r,c and setB contains 1,2,3,r, and I want the union and intersection of these two sets, which means don't print repeatedly if the element is in both setA and setB)