@fermatslibrary - Anagram finder implemented using Prime Numbers in Rust

prime_anagrams.rs

// Courtesy: @Fermatslibrary
// Reference: https://twitter.com/fermatslibrary/status/1275066521450975234
// Copyright: Anand B Pillai @skeptichacker
// LICENSE: MIT

use std::env;
use std::collections::HashMap;

pub fn is_prime(n: u64)  -> bool {

    if n <= 1 {
        return false;
    }
            
    let mut flag = true;
    let mut item: u64 = 2;

    loop {
        if item*item > n { break; }
        if n % item == 0 {
            flag = false;
            break;
        }
        item += 1;
    }
        
    return flag;
}

pub fn get_prime_factors(n: u64) -> Vec<u64> {

    let mut p: u64 = 3;
    let mut factors: Vec<u64> = vec![];

    if n % 2 == 0 {
        factors.push(2);
    }
    
    loop {
        if n % p == 0 && is_prime(p) {
            factors.push(p);
        }

        if p >= n/2 { break; }
        p += 2;
    }
        
    return factors;
}

fn prime_map() -> HashMap<char, u64> {

    let mut alpha_hash: HashMap<char, u64> = HashMap::new();
    let alphas:Vec<char> = "abcdefghijklmnopqrstuvwxyz".chars().collect();
    let mut n: u64 = 3;

    alpha_hash.insert('a', 2);
    
    for alpha in alphas.iter() {
        if *alpha == 'a' { continue; }
        while !is_prime(n) {
            n += 2;
        }
        alpha_hash.insert(*alpha, n);
        n += 2;
    }

    println!("{:?}", alpha_hash);

    return alpha_hash;
}

fn main() {

    // Pass two strings into the program
    let args: Vec<String> = env::args().collect();

    let word1 = &args[1];
    let word2 = &args[2];

    println!("Words are {} and {}", word1, word2);
    // Build alpha->primes map
    let _alpha_prime = prime_map();

    // Get word1 -> prime factors product
    let _prod1 = word1.chars().map(|c| _alpha_prime.get(&c)).fold(1, |p, x| p*x.unwrap());
    let _prod2 = word2.chars().map(|c| _alpha_prime.get(&c)).fold(1, |p, x| p*x.unwrap());
    if _prod1 == _prod2 {
        println!("Yes: anagrams");
    } else {
        println!("Nope: nanagrams");
    }

}