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I wrote a C++ program that prints all prime numbers lower than n, but the program keeps crashing while executing.

#include <iostream> using namespace std; bool premier(int x) { int i = 2; while (i < x) { if (x % i == 0) return false; i++; } return true; } int main() { int n; int i = 0; cout << "entrer un entier n : "; cin >> n; while (i < n) { if (n % i == 0 && premier(i)) cout << i; i++; } ; }
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  • 1
    The right tool for investigating this is a debugger. Commented Oct 22, 2017 at 3:39
  • 6
    You execute n % i with i == 0 Commented Oct 22, 2017 at 3:40
  • start at i=1 instead Commented Oct 22, 2017 at 3:44
  • 1
    start with n % i with i = 2 Commented Oct 22, 2017 at 3:46

1 Answer 1

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As Igor pointed out, i is zero the first time when n%i is done. Since you want only prime numbers and the smallest prime number is 2, I suggest you initialise i to 2 instead of 0.

You want to print all prime numbers less than n and has a function to check primality already.

Just 

while (i < n){ if ( premier(i) == true ) cout<<i; i++; }

And while printing, add a some character to separate the numbers inorder to be able to distinguish them like

cout<<i<<endl;

P.S: I think you call this a C++ program. Not a script.

Edit: This might interest you.

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