How can I remove the last comma from a loop in C++ in a simple way?

Question

This program is for printing prime numbers till the input given and separating every prime number with a comma.

void main(){

    int N, counter=0, isPrime;
         


        

Answer 1

Just decide from a pre condition:

bool first = true;
for(j=2;j<=N;j++){
   // ...
   if(k==N) {
   if(!first) {
       cout << ',';
   }
   else {
       first = false;
   }
   cout<