Prime Factors of a number in C
Find Prime Factors of a number
Today in this article we will learn about how to find Prime Factors of a number .
Any natural number which is greater than 1 and has only two factors i.e., 1 and the number itself is called a prime number.
Lets understand this with the help of example :-
- Input:- 24
Output:- 2, 2, 2, 3
Here the prime factor of 24 is 2, 2, 2, 3 that is if we multiply 2*2*2*3 = 24. If the input number is 35 then the prime factors is equal to 5, 7.
Algorithm
- First take the number lets say num for which we need to find the factors.
- Make a function prime factors that will print all the factors of the number.
- Start the loop from i = 2 till the value of num > 1
- Inside the for loop make a while loop with condition (num%i == 0) this will check if i divides the number.
- Inside the while loop print the value of i and divide num by i.
Method 1 Code in C :-
Run
#include <stdio.h>
void primefactor(int num) {
printf("Prime factors of the number : ");
for (int i = 2; num > 1; i++) {
while (num % i == 0) {
printf("%d ", i);
num = num / i;
}
}
}
int main() {
int num;
num=12;
primefactor(num);
return 0;
}
Output:-
Enter the positive integer: 24 Prime factors of the number : 2 2 2 3
Finding Prime Factors of a number
Method 2 (Efficient)
- First Print the number of 2s that is n divisible by 2.
- After step 1, the value of n must be odd. Now start a loop from i = 3 till the square root of n. While i divides n, print i, and divide n by i.
- After i fails to divide n, increment i by 2 and continue.
- If n is a prime number and is greater than 2, then n will not become 1 by the above two steps.
- So print n if it is greater than 2.
Method 2 Code in C :-
Run
#include <stdio.h>
#include <math.h>
void primefactors(int n) {
// Print the number of 2s that divide n
while (n % 2 == 0) {
printf("%d ", 2);
n = n / 2; }
// n must be odd at this point. So we can skip ne element (Note i = i +2)
for (int i = 3; i <= sqrt(n); i = i + 2) {
// While i divides n, print i and divide n
while (n % i == 0) {
printf("%d ", i);
n = n / i;
}
}
//This condition is to handle the case when n is a prime number greater than 2
if (n > 2) {
printf("%d ", n);
}
int main() {
int number = 24;
printf("Prime factor of the number: ");
primefactors(number);
return 0;
}
Output:-
Prime factor of the number: 2 2 2 3
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Very easy answer
#include
int main()
{
int number = 24;
int temp=number;
for(int i=2;i<=temp/2;i++)
{
if(number%i==0)
{
printf("%d ",i);
number=number/i;
i–;
}
}
}
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