Euler3.rs

/*

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

Answer:


*/

fn is_prime(num : u64 ) -> bool{
    if num == 1 {
        return true;
    }
    
    if num < 1 {
        return false;
    }
    
    for i in 2..num{
        if num % i == 0 && i != num {
            return false;                    
        }
    }
    return true;
}


fn get_largest_prime_factor(num : u64) -> u64 {
    println!("Entering prime ");
    let mut largest_pf :u64 = 2;
    let mut next_pf : u64 = 2;
    
    loop{
        if next_pf < num && num % next_pf == 0 && is_prime(next_pf){
            largest_pf = next_pf;
            
        }else if next_pf >= num {
            break;
        }
        
        next_pf += 1;
     
    }
    largest_pf
    
    
}
fn main(){
    // let mut p = 1;
   
    // loop {
    //     p += 1;
    //     if is_prime(p) {
    //         println!("Prime number {}",p);
    //     }
    //     if p > 21{
    //         break;
    //     }
    // }
    
    // println!("{}", p);
    println!("Calling prime ");
    
    // Still not resolved for such large integer
    let largest_pf = get_largest_prime_factor(600851475143 );
    println!("{}", largest_pf);
}