Day 14

3 files changed, 166 insertions, 0 deletions

diff --git a/day14/Cargo.toml b/day14/Cargo.toml
new file mode 100644
index 0000000..d2891da
--- /dev/null
+++ b/day14/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "day14"
+version = "0.1.0"
+authors = ["Federico Igne <git@federicoigne.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/day14/resources/input.txt b/day14/resources/input.txt
new file mode 100644
index 0000000..5074877
--- /dev/null
+++ b/day14/resources/input.txt
@@ -0,0 +1,102 @@
+SCVHKHVSHPVCNBKBPVHV
+
+SB -> B
+HH -> P
+VF -> N
+BS -> S
+NC -> C
+BF -> H
+BN -> H
+SP -> H
+BK -> H
+FF -> N
+VN -> B
+FN -> C
+FS -> S
+PP -> F
+ON -> H
+FV -> F
+KO -> F
+PK -> H
+VB -> S
+HS -> B
+NV -> O
+PN -> S
+VH -> B
+OS -> P
+BP -> H
+OV -> B
+HK -> S
+NN -> K
+SV -> C
+PB -> F
+SK -> F
+FB -> S
+NB -> K
+HF -> P
+FK -> K
+KV -> P
+PV -> F
+BC -> S
+FO -> N
+HC -> F
+CP -> B
+KK -> F
+PC -> S
+HN -> O
+SH -> H
+CK -> P
+CO -> F
+HP -> K
+PS -> C
+KP -> F
+OF -> K
+KS -> F
+NO -> V
+CB -> K
+NF -> N
+SF -> F
+SC -> P
+FC -> V
+BV -> B
+SS -> O
+KC -> K
+FH -> C
+OP -> C
+CF -> K
+VO -> V
+VK -> H
+KH -> O
+NP -> V
+NH -> O
+NS -> V
+BH -> C
+CH -> S
+CC -> F
+CS -> P
+SN -> F
+BO -> S
+NK -> S
+OO -> P
+VV -> F
+FP -> V
+OK -> C
+SO -> H
+KN -> P
+HO -> O
+PO -> H
+VS -> N
+PF -> N
+CV -> F
+BB -> H
+VC -> H
+HV -> B
+CN -> S
+OH -> K
+KF -> K
+HB -> S
+OC -> H
+KB -> P
+OB -> C
+VP -> C
+PH -> K
diff --git a/day14/src/main.rs b/day14/src/main.rs
new file mode 100644
index 0000000..6cca304
--- /dev/null
+++ b/day14/src/main.rs
@@ -0,0 +1,55 @@
+use std::fs;
+use std::path::Path;
+use std::collections::HashMap;
+use std::iter::FromIterator;
+
+type Expand = (char,char);
+type Rules = HashMap<(char,char),char>;
+type Frequency = HashMap<char,u128>;
+type FrequencyMap = HashMap<Expand,Frequency>;
+
+/* AOC21 Day 14: https://adventofcode.com/2021/day/14 */
+fn main() {
+    let input = Path::new("resources").join("input.txt");
+    let content = fs::read_to_string(input).expect("Unable to read input file");
+    let (template,rules) = content.split_once("\n\n").expect("Malformed input");
+    let rules = Rules::from_iter(rules.lines().map(|l| {
+        let (from,to) = l.split_once(" -> ").expect("Malformed input");
+        let chars = from.chars().collect::<Vec<char>>();
+        ((chars[0],chars[1]),to.parse().unwrap())
+    }));
+    let mut frequency = FrequencyMap::new();
+    rules.iter().for_each(|(&(a,b),&c)| {
+        let mut map = HashMap::new(); map.insert(c,1);
+        frequency.insert((a,b),map);
+    });
+    (1..10).for_each(|_| frequency = expand(&frequency, &rules));
+    println!("Ex1: the result is {}", template_frequency(template, &frequency));
+    (0..30).for_each(|_| frequency = expand(&frequency, &rules));
+    println!("Ex2: the result is {}", template_frequency(template, &frequency));
+}
+
+fn expand(frequency: &FrequencyMap, rules: &Rules) -> FrequencyMap {
+    let mut freq2 = FrequencyMap::new();
+    rules.iter().for_each(|(&(a,b),&c)| {
+        let mut map = merge(frequency.get(&(a,c)).unwrap(), frequency.get(&(c,b)).unwrap());
+        *map.entry(c).or_default() += 1;
+        *freq2.entry((a,b)).or_default() = map;
+    });
+    freq2
+}
+
+fn template_frequency(template: &str, frequency: &FrequencyMap) -> u128 {
+    let mut freq = HashMap::new();
+    template.chars().for_each(|c| *freq.entry(c).or_default() += 1);
+    freq = template.chars().collect::<Vec<char>>()
+                   .as_slice().windows(2)
+                   .fold(freq, |acc, w| merge(&acc, frequency.get(&(w[0],w[1])).unwrap()) );
+    freq.values().max().unwrap() - freq.values().min().unwrap()
+}
+
+fn merge(a: &Frequency, b: &Frequency) -> Frequency {
+    let mut map = a.clone();
+    b.iter().for_each(|(&k,&v)| *map.entry(k).or_default() += v);
+    map
+}