Question

How to calculate the Nth prime number in Rust

Answer 1

// 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73

fn get_the_nth_prime_number(nth: usize) -> usize {
    let mut prime = 1;
    let mut count = 0;

    while count < nth {
        prime += 1;
        let mut savedi = 0;
        for i in 2..= prime {
            if prime % i == 0 {
                savedi = i;
                break;
            }
        }
        if (savedi == prime) {
            count += 1;
        }
    }

    prime
}

fn main() {
    let nth = 8;
    
    println!("Nth prime: {}", get_the_nth_prime_number(nth));
}


  
/*
run:
  
Nth prime: 19
  
*/

 

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Answer 2

// 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73

fn get_the_nth_prime_number(nth: usize) -> usize {
    let mut prime = 1;
    let mut count = 0;

    while count < nth {
        prime += 1;
        let mut is_prime = true;
        for i in 2..=prime {
            if prime % i == 0 && i != prime {
                is_prime = false;
                break;
            }
        }
        if is_prime {
            count += 1;
        }
    }

    prime
}

fn main() {
    let nth = 8;

    println!("Nth prime: {}", get_the_nth_prime_number(nth));
}


  
/*
run:

Nth prime: 19
  
*/

 

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