Determination of Prime Factors using Functions.

A positive integer is entered through the keyboard.
Write a function to obtain the prime factors of this number.
For example, prime factors of 24 are 2, 2, 2 and 3, whereas prime factors of 35 are 5 and 7.



#include<stdio.h>
main()
{

int number;
int prime(int number);

int primefactor(int number);


printf("Enter the number whose prime factors are to be calculated:");

scanf ("%d", &number);

primefactor(number);

}

//The following function detects a Prime number.

prime(int num)
{
int i, ifprime;


for (i=2; i<=num-1; i++)

{
if (num%i==0)
{

ifprime=0;
}
else
ifprime=1;

}
return (ifprime);
}


//The following function prints the prime factors of a number.

primefactor(int num)
{
int factor,ifprime;
for (factor=2; factor<=num;)

{
prime(factor); //so that the factors are only prime and nothing else.
if (ifprime)

{
if (num%factor==0) //diving by all the prime numbers less than the number itself.
{

printf("%d ", factor);
num=num/factor;

continue;
}
else
{
factor++;//this cannot be made a part of the for loop

}
}
}
return 0;
}





The file can be found at:
Download File

Comments

bbb said…
Another method using recursion:

void main()
{
int x;
printf("\nInput an integer\n");
scanf("%d",&x);
prime(x);
}

prime(int x)
{
int a;
for(a=2;a<=x;a++)
{
if(x%a==0)
{
printf("%d ",a);
prime(x/a);
break;
}
}
}
------------------------
jelly.fishinq@gmail.com
9:06 AM, October 02, 2009
bbb said…
without recursion

void main()
{
int x;
printf("\nInput an integer\n");
scanf("%d",&x);
prime(x);
}

prime(int x)
{
int a;

for(a=2;a<=x;a++)
{
if(x%a==0)
{
printf("%d ",a);
x/=a;
a--;
}
}
}
9:11 AM, October 02, 2009
surya said…
become a follower for free C,C++ And vb code of my blog:
http://www.a2zhacks.blogspot.com to learn C,C++,VB programming.
12:14 AM, January 05, 2010
Anonymous said…
bing chang good and short way
10:48 PM, November 14, 2011
Anonymous said…
Printing prime factors [Recursion method]


#include
#include
int pdetect (int x);
void primefactprint (int x);
void main()
{
int a;
clrscr();
printf("Enter positive integer to obtain its prime factors: ");
scanf("%d",&a);
printf("\nCalling function to obtain prime factors\n");
primefactprint(a);
printf("\nPress any key to exit");
getch();
}

int pdetect (int x)
{
int i,sum=0;
for (i=1;i<=x;i++)
{
if (x%i==0)
{
sum++;
}
}
if (sum<=2)
{
return 1;
}
else
{
return 0;
}
}

void primefactprint (int x)
{
int j,primecondition;
for (j=1;j<=x;j++)
{
primecondition=pdetect(j);
if (primecondition==1)
{
if (x%j==0)
{
printf("\n%d",j);
}
}
}
}
6:45 AM, January 09, 2012
sumathi said…
#include
int pf(int x);
main()
{
int num, count;
printf("Enter the no\n");
scanf("%d",&num);
for (count=1;count<=num;count++)
{
if (num%count==0)
{
int prmfctr=pf(count);
}
}
return 0;
}
int pf(int x)
{
int c;
for (c=2;c<x;c++)
{
int pf=x%c;
if(pf==0)
goto step1;
}
printf("%d is a prime factor\n",x);
step1: printf("\n");
return (pf);
}
9:21 AM, April 27, 2012
Post a Comment

Popular posts from this blog

C Program - Calculation of Area and Circumference of a Circle using Pointers

The following program is one good example that illustrates how we can return more than one value in a function. The answer is certainly using Pointers. The following program demonstrates the method. Write a function that calculates both Area and Perimeter/ Circumference of the Circle, whose Radius is entered through the keyboard. #include <stdio.h> main ( ) { int radius ; float area , perimeter ; printf ( " \n Enter radius of a circle:" ) ; scanf ( "%d" , & radius ) ; areaperi ( radius , & area , & perimeter ) ; printf ( "Area=%f" , area ) ; printf ( " \n Perimeter=%f" , perimeter ) ; } areaperi ( int r , float * a , float * p ) { * a = 3.14 * r * r ; * p = 2 * 3.14 * r ; } // This Program exhibits the use of Call By Reference . The program can be found at: Download File.
Read more

Matchstick Game using C Programming

Write a program for a matchstick game being played between the computer and a user. Your program should ensure that the computer always wins. Rules for the game are as follows: -There are 21 matchsticks. -The computer asks the player to pick 1, 2, 3 or 4 matchsticks. -After the person picks, the computer does its picking. -Whoever is forced to pick up the last matchstick loses the game. -There are 21 matchsticks. -Whoever is forced to pick up the last matchstick loses the game. So the last one is special, so it's all about how to get rid of 20 matches in pairs of turns. -The computer asks the player to pick 1, 2, 3 or 4 matchsticks. So if we reduce the total by 5 each round, the sequence will go 21 16 11 6 1 In effect, whatever number the user picks (n), the computer picks 5-n #include <stdio.h> main ( ) { int matchsticks = 21 , user , computer ; printf ( "Do not enter Invalid Numbers. \n Numbers above 4 are invalid." ) ; printf ( " \n If you do so, t
Read more

Generation of Fibonacci Sequence using Recursion.

Write a recursive function to obtain the first 25 numbers of a Fibonacci sequence. In a Fibonacci sequence the sum of two successive terms gives the third term. Following are the first few terms of the Fibonacci sequence: 1 1 2 3 5 8 13 21 34 55 89 ... #include <stdio.h> main ( ) { static int prev_number = 0 , number = 1 ; // static : so value is not lost int fibonacci ( int prev_number , int number ) ; printf ( "Following are the first 25 Numbers of the Fibonacci Series: \n " ) ; printf ( "1 " ) ; // to avoid complexity fibonacci ( prev_number , number ) ; } fibonacci ( int prev_number , int number ) { static int i = 1 ; // i is not 0 , cuz 1 is already counted in main . int fibo ; if ( i = = 25 ) { printf ( " \n done" ) ; // stop after 25 numbers } else { fibo = prev_number + number ; prev_number = number ; // important steps number = fibo ; printf ( " \n %d" , fibo ) ; i + + ; // increment
Read more