feat: solve day 14 part 1

input/14.txt

@@ -0,0 +1,102 @@
+BVBNBVPOKVFHBVCSHCFO
+
+SO -> V
+PB -> P
+HV -> N
+VF -> O
+KS -> F
+BB -> C
+SH -> H
+SB -> C
+FS -> F
+PV -> F
+BC -> K
+SF -> S
+NO -> O
+SK -> C
+PO -> N
+VK -> F
+FC -> C
+VV -> S
+SV -> S
+HH -> K
+FH -> K
+HN -> O
+NP -> F
+PK -> N
+VO -> K
+NC -> C
+KP -> B
+CS -> C
+KO -> F
+BK -> N
+OO -> N
+CF -> H
+KN -> C
+BV -> S
+OK -> O
+CN -> F
+OP -> O
+VP -> N
+OC -> P
+NH -> C
+VN -> S
+VC -> B
+NF -> H
+FO -> H
+CC -> B
+KB -> N
+CP -> N
+HK -> N
+FB -> H
+BH -> V
+BN -> N
+KC -> F
+CV -> K
+SP -> V
+VS -> P
+KF -> S
+CH -> V
+NS -> N
+HS -> O
+CK -> K
+NB -> O
+OF -> K
+VB -> N
+PS -> B
+KH -> P
+BS -> C
+VH -> C
+KK -> F
+FN -> F
+BP -> B
+HF -> O
+HB -> V
+OV -> H
+NV -> N
+HO -> S
+OS -> H
+SS -> K
+BO -> V
+OB -> K
+HP -> P
+CO -> B
+PP -> K
+HC -> N
+BF -> S
+NK -> S
+ON -> P
+PH -> C
+FV -> H
+CB -> H
+PC -> K
+FF -> P
+PN -> P
+NN -> O
+PF -> F
+SC -> C
+FK -> K
+SN -> K
+KV -> P
+FP -> B
+OH -> F

src/day14.rs

@@ -0,0 +1,88 @@
+use std::collections::HashMap;
+
+pub struct InsertionRule([char; 2], char);
+
+pub struct InputData {
+    polymer_template: String,
+    rules: Vec<InsertionRule>
+}
+
+fn parse_rule(line: &str) -> InsertionRule {
+    let (pattern, expansion) = line.split_once(" -> ").unwrap();
+    return InsertionRule(
+        [pattern.chars().nth(0).unwrap(), pattern.chars().nth(1).unwrap()],
+        expansion.chars().nth(0).unwrap()
+    );
+}
+
+pub fn parse_input(input: &str) -> InputData {
+    let (polymer_template, rules_section) = input.split_once("\n\n").unwrap();
+    let rules = rules_section.lines()
+        .map(parse_rule)
+        .collect();
+    return InputData {
+        polymer_template: polymer_template.into(),
+        rules
+    };
+}
+
+fn expand_polymer(polymer: Vec<char>, rules: &Vec<InsertionRule>) -> Vec<char> {
+    let mut new_polymer = Vec::new();
+    for i in 0..polymer.len()-1 {
+        new_polymer.push(polymer[i]);
+        for rule in rules {
+            if rule.0[0] == polymer[i] && rule.0[1] == polymer[i+1] {
+                new_polymer.push(rule.1);
+            }
+        }
+    }
+    new_polymer.push(*polymer.last().unwrap());
+    return new_polymer;
+}
+
+pub fn part1(input: &InputData) -> u32 {
+    let mut polymer = input.polymer_template.chars().collect();
+    for _ in 0..10 {
+        polymer = expand_polymer(polymer, &input.rules);
+    }
+
+    let mut element_amounts = HashMap::new();
+    for c in polymer {
+        let amount = element_amounts.entry(c).or_insert(0);
+        *amount += 1;
+    }
+
+    let least_common_element = element_amounts.iter().min_by(|a, b| a.1.cmp(b.1)).unwrap().1;
+    let most_common_element = element_amounts.iter().max_by(|a, b| a.1.cmp(b.1)).unwrap().1;
+    return most_common_element - least_common_element;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        let polymer_template = String::from("NNCB");
+        let rules = vec![
+            InsertionRule(['C', 'H'], 'B'),
+            InsertionRule(['H', 'H'], 'N'),
+            InsertionRule(['C', 'B'], 'H'),
+            InsertionRule(['N', 'H'], 'C'),
+            InsertionRule(['H', 'B'], 'C'),
+            InsertionRule(['H', 'C'], 'B'),
+            InsertionRule(['H', 'N'], 'C'),
+            InsertionRule(['N', 'N'], 'C'),
+            InsertionRule(['B', 'H'], 'H'),
+            InsertionRule(['N', 'C'], 'B'),
+            InsertionRule(['N', 'B'], 'B'),
+            InsertionRule(['B', 'N'], 'B'),
+            InsertionRule(['B', 'B'], 'N'),
+            InsertionRule(['B', 'C'], 'B'),
+            InsertionRule(['C', 'C'], 'N'),
+            InsertionRule(['C', 'N'], 'C')
+        ];
+        let result = part1(&InputData { polymer_template, rules });
+        assert_eq!(result, 1588);
+    }
+}

src/main.rs

@@ -11,6 +11,7 @@ mod day10;
 mod day11;
 mod day12;
 mod day13;
+mod day14;
 
 use std::{env, process};
 use std::fs::File;
@@ -53,6 +54,7 @@ fn run(day: i32, part: i32, input_filename: &str) {
         "12.2" => println!("{}", day12::part2(&day12::parse_input(&contents))),
         "13.1" => println!("{}", day13::part1(&day13::parse_input(&contents))),
         "13.2" => day13::part2(&day13::parse_input(&contents)),
+        "14.1" => println!("{}", day14::part1(&day14::parse_input(&contents))),
         _ => println!("Day {} part {} not found", day, part)
     }
 }