loops - How do I perform a duplicate check in code? -

this might no-brainer some, i'm trying check if there duplicate values in code.

to clearer, creating 5 variable integers randomizes number once created. let's they're named i1, i2, i3, i4, i5.

i want run loop check on each other make sure don't have possible duplicates. if do, i'll re-random second integer that's being checked. (e.g if (i1 == i4) { i4.rand(); }) that's make sure i1 doesn't need re-checked against checked values or being stuck in long loop until different number found.

this i'm thinking if entire if else statement : if (i1 == i2), if (i1 == i3), if (i1 == i4), if (i1 == i5), if (i2 == i3), if (i2 == i4), if (i2 == i5), if (i3 == i4), if (i3 == i5), if (i4 == i5)

i know can "manually" creating lots of if / else statements, there better way it? isn't feasible if increase integer limit 20 , have if / else way through 20 value checks. know there is, can't remember. search on google turning nothing (maybe i'm searching wrong keywords), why i'm asking on here @ stackoverflow.

all want know how do it, theory-wise (how check duplicates in theory?). answer doesn't need workable function.

if want create demo code using programming language i'm using problem, itsexcel vba. think information able apply theory-wise lot of other programming languages, feel free write in javascript/jquery, c++, c#, etc. remember comment!

you looking set;

    set<integer> hs = new hashset<integer>();     hs.add(i1);     if(!hs.add(i2)){        randomize(i2);     } 

hope helps. let me know, if have questions. above concept of do.

to logic code, be

   set<integer> hs = new hashset<integer>();      for(int count=0; count<array.length; count++){  // store data array , loop         datatoinsert = array[count];           while(hs.add(datatoinsert)){            datatoinsert = randomize(datatoinsert);         }      }