Advent 2023 Day 4

advent_of_code_2023/day4/main2.rs

@@ -0,0 +1,49 @@
+use std::cmp::min;
+use std::fs::read_to_string;
+use std::collections::HashSet;
+
+struct Card {
+    numbers: Vec<i32>,
+    winners: HashSet<i32>
+}
+
+fn count_wins(card: &Card) -> usize {
+    let mut hits = 0;
+
+    for number in &card.numbers {
+        if card.winners.contains(&number) {
+            hits += 1;
+        }
+    }
+
+    hits
+}
+
+fn main() {
+    let cards = read_to_string("input.txt").unwrap().lines().map(|line| {
+        let (_, card) = line.split_once(':').unwrap();
+        let (numbers, winners) = card.split_once('|').unwrap();
+        
+        let numbers = numbers.split(' ').filter(|numstr| { !numstr.is_empty() }).map(|number| {
+            number.parse::<i32>().unwrap()
+        }).collect::<Vec<_>>();
+
+        let winners = winners.split(' ').filter(|numstr| { !numstr.is_empty() }).map(|number| {
+            number.parse::<i32>().unwrap()
+        }).collect::<HashSet<_>>();
+
+        Card{numbers: numbers, winners: winners}
+    }).collect::<Vec<_>>();
+
+    let mut stacks = vec![1; cards.len()];
+
+    for idx in 0..stacks.len() {
+        let score = count_wins(&cards[idx]);
+
+        for wins in (idx + 1)..min(idx + score + 1, stacks.len()) {
+            stacks[wins] += stacks[idx];
+        }
+    }
+
+    println!("Total #cards: {}", stacks.iter().sum::<i32>());
+}