aoc_2023/day07/aoc.rs

use std::iter::*;
use std::cmp::*;
use std::collections::HashMap;
use std::fs;
use std::env;


type Hand = [usize;5];

fn main() {
	let card_value: HashMap<char, usize> = zip([ '2', '3', '4', '5', '6', '7', '8', '9', 'T', 'J','Q', 'K', 'A'], 0..13).collect();

	println!("Hello, AoC day 7!");

	let args: Vec<String> = env::args().collect();
	if args.len() != 2 {
		println!("wrong number of arguments!");
		std::process::exit(1);
	}

	let file_path = &args[1];

	// get time lineaswords and distance line as words
	let binding = fs::read_to_string(file_path)
		.expect("Should have been able to read the file");
	let contents = binding.lines();

	let mut hands: Vec<(Hand, u32)> = Vec::new();

	for line in contents {
		if !line.is_empty() {
			hands.push(parse(line, &card_value));
		}
	}
	
	hands.sort_unstable_by(|(ha, _), (hb, _)| hand_compare(*ha, *hb));

	let mut sum = 0;
	for (index, (_hand, bet)) in hands.iter().enumerate() {
		let score = ((index as u32) + 1) * bet;
		sum += score;
	}

	println!("total scores was: {}", sum);
}

fn parse(line: &str, dictionary: &HashMap<char, usize>) -> (Hand, u32) {
	let (hand, value) = line.split_once(" ").expect("expected a line to have the format 'AAAAA ###'");
	let mut m: [usize;5] = [0;5];

	for (i, character) in hand.chars().enumerate() {
		m[i] = *dictionary.get(&character).expect(&format!("expected a card in {}", line));
	}

	let val:u32 = value.parse().unwrap();
	println!("{:?} for {}", m, val);
	return (m, val);
}

fn rank(hand: Hand) -> u32 {
	let mut a = [0; 13];
	for letter in hand {
		a[letter] += 1;
	}
	
	let mut fives = 0;
	let mut fours = 0;
	let mut threes = 0;
	let mut twos = 0;
	let mut _ones = 0;

	for number in a {
		match number {
			5 => fives += 1,
			4 => fours += 1,
			3 => threes += 1,
			2 => twos += 1,
			1 => _ones += 1,
			_ => ()
		}
	}

	if fives > 0 {
		return 6;
	}
	if fours > 0 {
		return 5;
	}
	if threes == 1 && twos == 1 {
		return 4;
	}
	if threes == 1 {
		return 3;
	}
	if twos == 2 {
		return 2;
	}
	if twos == 1 {
		return 1;
	}

	return 0;
}


fn hand_compare(a: Hand, b: Hand) -> Ordering {
	let bs_a = rank(a);
	let bs_b = rank(b);

	if bs_a > bs_b {
		return Ordering::Greater;
	} else if bs_a < bs_b {
		return Ordering::Less;
	}

	if a > b {
		return Ordering::Greater;
	} else if a < b {
		return Ordering::Less;
	}

	return Ordering::Equal;
}