Question

I want to compare each item in an array to every other item in said array. I’m doing this at the moment, is it ok or is there a prettier/faster/more logical way of doing it?

for(int i=0; i<array1.size(); i++){
  for(int j=0; j<array1.size(); j++){
    if(i!=j){
      ..do stuff..
    }
  }
}

Answer 1

You’re doing too many comparisons, plus you’re comparing every item to itself needlessly. What you want is this:

for(int i=0; i<array1.size(); i++){
  for(int j=i + 1; j<array1.size(); j++){
     if(arr[i] != arr[j]){
        ..do stuff..
     }
  }
}

(This is assuming that your idea of equality is commutative, which equality normally is.)

If there are N items in your array, your original snippet would be doing N^2 comparisons, whereas my snippet is doing N(N-1)/2 comparisons.