CODEWITHSUNDEEP
cloops
KhalidGT
KhalidGT

Reputation: 51

program going into infinite loop after 15 seconds

I am making a program to find prime factorials of a given number.
Although the program works fine, I have two problems.
1. when i enter an odd number, it prints 2 in the result although 2 should not be in it.
2. After 15 seconds , it turns into an infinite loop , Which is really creepy.

#include<stdio.h>
#include<conio.h>
int num(int); // Making a function for finding prime factors
int main()
{
    int i,j;
    printf("Enter any number");
    scanf("%d",&i);
    num(i);

    getch();

    }

int num(int i)
{

    int a=2;
    while(a<=i)
    {

        if(i%a==0) //if the number is divisible then divide it
            i=i/a;

        printf(" %d",a);

        if(i%a!=0) 
       {
            i%a;
            while(i%a!=0)// If it is not divisible by 2 then increment it until it is
                 a++;
       }

    }

}

Upvotes: 1

Views: 130

Answers (2)

Fred
Fred

Reputation: 8602

It always prints 2 because the print statement is not part of the if which tests for mod 0. It goes into an infinite loop because once a passes i, the second while loop will never exit.

Upvotes: 4

Scott Mermelstein
Scott Mermelstein

Reputation: 15397

The infinite loop is your second while loop, while(i%a!=0). For a prime number, this will continue endlessly. There are smart ways to fix that, but at the very least, change it to

while(i%a!=0 && a<=i)

I'm not sure why 2 is coming up on odd numbers, still thinking that part through.

EDIT As Fred mentioned, the printout is not part of the if statement, causing 2 to always show up. Personally, I recommend getting into the habit of always putting { } after an if statement. Even if you've been coding for decades, this will make sure you get the right statements in your condition.

Upvotes: 2

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