Advent of Code 2024, Day 1

2024/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "aoc-2024"
+version = "0.1.0"

2024/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "aoc-2024"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

2024/src/day1.rs

@@ -0,0 +1,157 @@
+use std::collections::HashMap;
+
+const INPUT: &'static str = include_str!("../data/day1.txt");
+
+pub fn day1a() -> String {
+    let (left_list, right_list) = parse_lists(INPUT);
+
+    let left_list = sort_list_asc(left_list);
+    let right_list = sort_list_asc(right_list);
+
+    let zipped = zip_lists(left_list, right_list);
+
+    format!("{}", total_distance(zipped))
+}
+
+pub fn day1b() -> String {
+    let (left_list, right_list) = parse_lists(INPUT);
+    format!("{}", total_similarity(left_list, right_list))
+}
+
+fn total_distance(pairs: Vec<(i32, i32)>) -> i32 {
+    pairs.into_iter().fold(0, |acc, pair| acc + distance(pair))
+}
+
+fn total_similarity(left_list: Vec<i32>, right_list: Vec<i32>) -> i32 {
+    let left_frequency = frequency_count(left_list);
+    let right_frequency = frequency_count(right_list);
+
+    let mut similarity = 0;
+
+    for (key, count) in left_frequency.into_iter() {
+        let right_occurences = right_frequency.get(&key).cloned().unwrap_or(0);
+
+        println!("[{}] {} * {}", key, count, right_occurences);
+
+        similarity += key * count * right_occurences;
+    }
+
+    similarity
+}
+
+fn distance(pair: (i32, i32)) -> i32 {
+    (pair.0 - pair.1).abs()
+}
+
+fn parse_lists(input: &str) -> (Vec<i32>, Vec<i32>) {
+    let mut left_list = vec![];
+    let mut right_list = vec![];
+
+    input.lines().for_each(|text| {
+        let values = text.split(' ').filter(|t| !t.is_empty()).map(|t| t.parse::<i32>().unwrap()).collect::<Vec<i32>>();
+        left_list.push(values[0]);
+        right_list.push(values[1]);
+    });
+
+    (left_list, right_list)
+}
+
+fn sort_list_asc(mut input: Vec<i32>) -> Vec<i32> {
+    input.sort();
+    input
+}
+
+fn zip_lists(left: Vec<i32>, right: Vec<i32>) -> Vec<(i32, i32)> {
+    left.into_iter().zip(right).collect::<Vec<(i32, i32)>>()
+}
+
+type FrequencyCount = HashMap<i32, i32>;
+
+fn frequency_count(lst: Vec<i32>) -> FrequencyCount {
+    let mut cnt = HashMap::new();
+
+    for number in lst {
+        cnt.entry(number).and_modify(|e| {*e += 1; }).or_insert(1);
+    }
+
+    cnt
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const TEST_INPUT: &'static str = "3   4
+4   3
+2   5
+1   3
+3   9
+3   3";
+
+    #[test]
+    fn it_figures_out_smallest_numbers() {
+        let (left_list, right_list) = parse_lists(TEST_INPUT);
+
+        assert_eq!(left_list.len(), 6);
+        assert_eq!(right_list.len(), 6);
+
+        assert_eq!(left_list, vec![3, 4, 2, 1, 3, 3]);
+        assert_eq!(right_list, vec![4, 3, 5, 3, 9, 3]);
+
+        let left_list = sort_list_asc(left_list);
+        let right_list = sort_list_asc(right_list);
+
+        assert_eq!(left_list[0], 1);
+        assert_eq!(right_list[0], 3);
+    }
+
+    #[test]
+    fn it_zips_two_lists() {
+        let (left_list, right_list) = parse_lists(TEST_INPUT);
+
+        let left_list = sort_list_asc(left_list);
+        let right_list = sort_list_asc(right_list);
+
+        let zipped = zip_lists(left_list, right_list);
+
+        assert_eq!(zipped[0], (1, 3));
+        assert_eq!(zipped[1], (2, 3));
+        assert_eq!(zipped[2], (3, 3));
+        assert_eq!(zipped[3], (3, 4));
+        assert_eq!(zipped[4], (3, 5));
+        assert_eq!(zipped[5], (4, 9));
+    }
+
+    #[test]
+    fn it_finds_difference_between_pairs() {
+        let (left_list, right_list) = parse_lists(TEST_INPUT);
+
+        let left_list = sort_list_asc(left_list);
+        let right_list = sort_list_asc(right_list);
+
+        let zipped = zip_lists(left_list, right_list);
+
+        assert_eq!(distance(zipped[0]), 2);
+        assert_eq!(distance(zipped[1]), 1);
+
+        assert_eq!(total_distance(zipped), 11);
+    }
+
+    #[test]
+    fn it_counts_frequencies() {
+        let (left_list, _right_list) = parse_lists(TEST_INPUT);
+
+        let frequencies = frequency_count(left_list);
+
+        assert_eq!(frequencies.get(&1), Some(&1));
+        assert_eq!(frequencies.get(&2), Some(&1));
+        assert_eq!(frequencies.get(&3), Some(&3));
+        assert_eq!(frequencies.get(&4), Some(&1));
+    }
+
+    #[test]
+    fn it_calculates_total_similarity() {
+        let (left_list, right_list) = parse_lists(TEST_INPUT);
+        assert_eq!(total_similarity(left_list, right_list), 31);
+    }
+}

2024/src/main.rs

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+mod day1;
+
+fn main() {
+    let day = std::env::args().skip(1).next();
+
+    let result = match day.as_ref().map(|v| v.as_ref()) {
+        Some("1a") => day1::day1a(),
+        Some("1b") => day1::day1b(),
+        _ => panic!("unrecognized day"),
+    };
+
+    println!("[{}] {}", day.unwrap(), result);
+}

rust-toolchain

@@ -1,3 +1,2 @@
 [toolchain]
-channel = "1.73.0"
+channel = "1.81.0"
-targets = [ "wasm32-unknown-unknown" ]