Thread: Finding The Biggest Prime Factor Of a Number

Hello i want to write a program which find the biggest prime factor of a number for example the biggest prime factor of six is three or the biggest prime factor of fifteen is five

This is my Code please tell me what is my program bug

Code:

#include <stdio.h>              // main functions
#include <math.h>               // for sqrt function
int main()
{
  int i, j, k, f;               // F = Flag;

  printf("Enter K\n\n");        // The Number which we want to scan
  scanf("%d", &k);              // Scanning Number
  for (i = 2; i < k; i++)       // loop for factors
  {

    if (k % i == 0) {
      for (j = 1; j < sqrt(i); j++) //prime loop
        if (i % j == 0) {
          printf("%d\n\n", i);
        }

    }



  }

  return 0;                     //Check if the program has work correctly & Finish
}

1. Cutting and pasting error
2. Laziness based on your lack of effort to fix the posted code.
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Tim S.

> This is my Code please tell me what is my program bug
Based on what is posted, I'd say it's on line 1.

Code:

PEBKAC

User error - Wikipedia, the free encyclopedia

Originally Posted by thedardwhie

what should i do to make my program complete and it give me the true answer

I don't like handing out complete solutions, but in your case, I'll make an exception.

Code:

#include <stdio.h>

int main()
{
  printf("42\n");
  return 0;
}

i mean what should i do to make my program complete and it give me the true answer

O_o

If you'd followed any of the advice you've been given in response to your shotgun approach to requesting help, you would actually be getting help instead being teased about your ridiculous threads.

Care to try, for example, posting formatted code?

Soma

> int i, j, k, f; // F = Flag;
I suggest you change the code to be this then.
int i, j, k, flag;

> printf("%d\n\n", i);
If your intent is to find the biggest, shouldn't you be doing something like checking all the factors, then printing out the biggest one found?

An idea might be to run your inner loop in reverse, then print the first one (hence the largest).