Chapter - 6: Functions And Pointers

A positive integer is entered through the keyboard. Write a function to obtain the prime factors of this number. Modify the function suitably to obtain the prime factors recursively.


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Sections
4
Exercises

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B

C

D

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G

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

void nonrec_pf(int);
int check_prime(int);
void rec_pf(int);
int main()
{
	rec_pf(24);
	printf("\n");
	nonrec_pf(35);
	_getch();
	return 0;

}

//non recursive function
void nonrec_pf(int num)
{
	int i;
	for (i = 2; num != 1; i++) //loop for obtaining the numbers.
	{
		if (num%i != 0)
			continue;
		else
		{
			if (check_prime(i) == 1)
			{
				while (num%i == 0)
				{
					printf("%d, ", i);
					num /= i;
				}
			}
		}
	}
}

//recursive function
void rec_pf(int num)
{
	int i;
	if (num == 0)
		return;

	for (i = 2; i <= num; i++)
	{
		if (num%i != 0)
			continue;
		else
		{
			if (check_prime(i) == 1)
			{
				printf("%d, ", i);
				rec_pf(num / i);
				return;
			}
		}
	}

}

//returns 1 if prime, otherwise 0.
int check_prime(int num)
{
	int i = 2;
	while (i < num)
	{
		if (i%num == 0)
			break;
		i++;
	}
	if (i == num)
		return 1;
	return 0;
}

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