Code to enumerate poker hands with two pairs from 5 cards out of a 52 card deck

poker.rs

use std::collections::HashMap;

fn is_two_pairs(c1: u32, c2: u32, c3: u32, c4: u32, c5: u32) -> bool {
    let mut hand: HashMap<u32, u32> = HashMap::new();
    *hand.entry(c1 % 13).or_insert(0) += 1;
    *hand.entry(c2 % 13).or_insert(0) += 1;
    *hand.entry(c3 % 13).or_insert(0) += 1;
    *hand.entry(c4 % 13).or_insert(0) += 1;
    *hand.entry(c5 % 13).or_insert(0) += 1;
    if (hand.len() != 3) {
        return false;
    }
    let mut values: Vec<&u32> = hand.values().collect();
    values.sort();
    return (*values[2] == 2);
}

fn main() {
    // A card is a number form 0 to 51.
    // Ace of spade = 0; Two if spade = 1; ..... ; King of club = 51. 
    const DECK: u32 = 13 * 4;
    let mut all_hands = 0;
    let mut two_pairs = 0;

    for i in 0..DECK {
        for j in (i..DECK).filter(|x| *x != i) {
            for k in (j..DECK).filter(|x| *x != i && *x != j) {
                for l in (k..DECK).filter(|x| *x != i && *x != j && *x != k) {
                    for m in (l..DECK).filter(|x| *x != i && *x != j && *x != k && *x != l) {
                        // println!("{} {} {} {} {}", i, j, k, l, m);
                        all_hands += 1;
                        if is_two_pairs(i, j, k, l, m) {
                            two_pairs += 1;
                        }
                    } // m
                } // l
            } // k
        } // j
    }  // i
    println!("{}", all_hands);
    println!("{}", two_pairs);

} // main()