calgorithmnumbersperformancefactors

Algorithm to find all the exact divisors of a given integer


I want to find all the exact divisors of a number. Currently I have this:

{
   int n;
   int i=2;
   scanf("%d",&n);
   while(i<=n/2)
    {
        if(n%i==0)
                  printf("%d,",i);
        i++;
     }
   getch();
}

Is there any way to improve it?


Solution

  • First, your code should have the condition of i <= n/2, otherwise it can miss one of the factors, for example 6 will not be printed if n=12.

    Run the loop to the square root of the number (ie. i <= sqrt(n)) and print both i and n/i (both will be multiples of n).

    {
       int n;
       int i=2;
       scanf("%d",&n);
       while(i <= sqrt(n))
        {
            if(n%i==0) {
                printf("%d,",i);
                if (i != (n / i)) {
                    printf("%d,",n/i);
                }
            } 
    
            i++;
        }
       getch();
    }
    

    Note :