Find prime factors of a number – Computer Sir Ki Class Code Learning #CPP#3218    ## Find prime factors of a number

Finding prime factors of a number input by the user.

## Learning Objectives

• Finding factors of number up to a level where all factors are prime.

## Source Code

 #include using namespace std; int main() { int n; cout<<"Enter a positive integer: "; cin>>n; cout<<"The prime factors are: "; for (int i=2; i <= n; i++) { while(n % i == 0) { n /= i; cout<

## Run Output

``````Enter a positive integer: 1224
The prime factors are: 2 2 2 3 3 17
``````

## Code Understanding

int n; cout<<“Enter a positive integer: “; cin>>n;
Collecting the input number from the user.

cout<<“The prime factors are: “; //Prompt before printing
for (int i=2; i <= n; i++) //Begins from 2 as no prime factor can not be less than 2
{
while(n % i == 0) //This loop works till the factor is identified
{
n /= i;                  //When identified the number is reduced by dividing with identified number
cout<<i<<” “; //Identified number is printed.
}
}

## Notes

• This code can be modified slightly to get prime factor only once.
• One can also modified it to store prime-factor in an array and then manipulate the array as required.
• Every positive integer number can be reduced to its prime factors because after reducing to prime factor further factorisation would not be possible, as a prime number is divisible by 1 and the number itself.

Suggested Filename(s): primefac.cpp

sunmitra| Created: 31-Jan-2018 | Updated: 15-Sep-2018|

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