feat: add day 4 - part 1

day_4/src/lib.rs

@@ -0,0 +1,132 @@
+use std::str::FromStr;
+
+#[derive(Debug, Default, PartialEq)]
+pub struct CardNumbers {
+    pub numbers: Vec<u32>,
+}
+
+impl FromStr for CardNumbers {
+    type Err = &'static str;
+
+    /// Parses a string `string` to return a value of [`CardNumbers`]
+    ///
+    /// If parsing succeeds, return the value inside [`Ok`], otherwise
+    /// when the string is ill-formatted return an error specific to the
+    /// inside [`Err`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::str::FromStr;
+    /// use day_4::CardNumbers;
+    ///
+    /// let string = "83 86  6 31 17  9 48 53";
+    /// let expected_result = CardNumbers {
+    ///     numbers: vec![83, 86, 6, 31, 17, 9, 48, 53],
+    /// };
+    /// let actual_result = CardNumbers::from_str(string).unwrap();
+    ///
+    /// assert_eq!(actual_result, expected_result);
+    /// ```
+    fn from_str(string: &str) -> Result<Self, Self::Err> {
+        let result = CardNumbers {
+            numbers: string
+                .split_whitespace()
+                .map(|string| string.trim())
+                .filter(|&string| !string.is_empty())
+                .map(|string| string.parse::<u32>().unwrap_or_default())
+                .collect(),
+        };
+        Ok(result)
+    }
+}
+
+#[derive(Debug, Default, PartialEq)]
+pub struct Card {
+    pub id: usize,
+    pub winning_numbers: CardNumbers,
+    pub owned_numbers: CardNumbers,
+}
+
+impl FromStr for Card {
+    type Err = &'static str;
+
+    /// Parses a string `string` to return a value of [`Card`]
+    ///
+    /// If parsing succeeds, return the value inside [`Ok`], otherwise
+    /// when the string is ill-formatted return an error specific to the
+    /// inside [`Err`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::str::FromStr;
+    /// use day_4::{Card, CardNumbers};
+    ///
+    /// let string = "Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53";
+    /// let expected_result = Card {
+    ///     id: 1,
+    ///     winning_numbers: CardNumbers { numbers: vec![41, 48, 83, 86, 17], },
+    ///     owned_numbers: CardNumbers { numbers: vec![83, 86, 6, 31, 17, 9, 48, 53], },
+    /// };
+    /// let actual_result = Card::from_str(string).unwrap();
+    ///
+    /// assert_eq!(actual_result, expected_result);
+    /// ```
+    fn from_str(string: &str) -> Result<Self, Self::Err> {
+        let mut result = Card::default();
+        let mut parts = string.split(": ");
+        result.id = parts
+            .next()
+            .unwrap_or("Card 1")
+            .strip_prefix("Card ")
+            .unwrap_or("1")
+            .parse()
+            .unwrap_or(1);
+
+        let mut numbers_parts = parts.next().unwrap_or("").split(" | ");
+
+        result.winning_numbers =
+            CardNumbers::from_str(numbers_parts.next().unwrap_or("")).unwrap_or_default();
+        result.owned_numbers =
+            CardNumbers::from_str(numbers_parts.next().unwrap_or("")).unwrap_or_default();
+
+        Ok(result)
+    }
+}
+
+pub fn part_1(input: &str) -> usize {
+    input
+        .lines()
+        .map(|line| Card::from_str(line).unwrap_or_default())
+        .map(|card| {
+            let numbers_matches_count = card
+                .owned_numbers
+                .numbers
+                .iter()
+                .filter(|&owned_number| card.winning_numbers.numbers.contains(owned_number))
+                .count() as u32;
+            let base: usize = 2;
+            if numbers_matches_count > 0 {
+                base.pow(numbers_matches_count.saturating_sub(1))
+            } else {
+                0
+            }
+        })
+        .sum::<usize>()
+}
+
+#[cfg(test)]
+mod day_4_tests {
+    use super::*;
+
+    #[test]
+    fn test_part_1_example() {
+        assert_eq!(part_1(include_str!("../input_example_1.txt")), 13);
+    }
+
+    // #[test]
+    // fn test_part_2_example() {
+    //     assert_eq!(part_2(include_str!("../input_example_1.txt")), 467835);
+    // }
+}

day_4/src/main.rs

@@ -0,0 +1,8 @@
+use day_4::part_1;
+
+fn main() {
+    let input = include_str!("../input.txt");
+    println!("- Day 4: Scratchcards -");
+    println!("Answer Part 1: {}", part_1(input));
+    // println!("Answer Part 2: {}", part_2(input));
+}