Thread: Decomposition of prime numbers (in C)

Hi, i am new in this, so please - be tolerant. Thanks
I was trying to figure this task out:

Task: Decomposition of prime numbers

The standard input is given a positive integer (the integer range). Determine the prime
decomposition of the given number (ie decomposition product of prime numbers) and write it to standard output as a product of prime factors with the power, as shown in the attached example. List primes in order from smallest to largest, do not write anywhere on the output gap.

Sample Input 1:

600

Corresponding output:

2 ^ 3 * 3 * 5 ^ 2

Sample Input 2:

1024

Corresponding output:

2 ^ 10

Sample Input 3:

77

Corresponding output:

7 * 11

My code (not working, don´t know why):

Code:

#include <stdio.h>
#include <conio.h>

void main(void)

{
 int number;
 int i, repeat, x;

 int primes[] = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997, 0};

 clrscr();

 printf("\nInput number:\n\n");

 scanf("%d", &number);
 fflush(stdin);

 printf("\n\nDecomposition of %d is ", number);

 i = 0;

 do{
	x = number;

	if(number == primes[i])
	  {
	   printf("%d", primes[i]);
	   getch();
	   return 1;
	  }

	if(number % primes[i] == 0)
	  {
	   printf("%d", primes[i]);
	   repeat = 0;
	   do{
		  number = number / primes[i];
		  repeat++;
		 } while(number % primes[i] != 0);

	   printf("^%d", repeat);
	  }

	if(number < primes[i + 1])
	  {
	   getch();
	   return 1;
	  }

	if(number != x)
	   printf("*");

	i++;
   } while(primes[i] != 0);
}

Any ideas? Load the source code please.

Ok, let's start from the beginning. Whomever is teaching you C doesn't really know any C him/herself.

1) void main(void) should be int main(void) and should return 0.
Cprogramming.com FAQ > main() / void main() / int main() / int main(void) / int main(int argc, char *argv[])

2) NEVER fflush(stdin). It's undefined behaviour.
Cprogramming.com FAQ > Why fflush(stdin) is wrong

3) You have the right idea, but the logic is a bit cluttered. I think it would be best if you moved some of the functionality, such as the one detecting how many times a prime number divides your number(prime^n) in another function and just return the value from there.