Question

How to check if a number is prime in Rust

Answer 1

use rand::Rng;
use std::f64;

fn is_prime(num: u32) -> bool {
    if num == 0 || num == 1 {
        return false;
    }
    
    for p in 2..= ((num as f64).sqrt() as u32) {
        if num % p == 0 {
            return false;
        }
    }
    
    true
}

fn main() {
    let mut rng = rand::thread_rng();
    
    for _ in 1..= 20 {
        let n = rng.gen_range(1..= 200);
        if is_prime(n) {
            println!("{} - Prime", n);
        } else {
            println!("{} - NOT Prime", n);
        }
    }
}



      
/*
run:
  
31 - Prime
167 - Prime
124 - NOT Prime
181 - Prime
11 - Prime
7 - Prime
99 - NOT Prime
196 - NOT Prime
124 - NOT Prime
7 - Prime
120 - NOT Prime
96 - NOT Prime
42 - NOT Prime
182 - NOT Prime
112 - NOT Prime
45 - NOT Prime
165 - NOT Prime
118 - NOT Prime
190 - NOT Prime
152 - NOT Prime
 
*/
 

 

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