add day 13

day13/src/main.rs

@@ -0,0 +1,83 @@
+use std::collections::HashSet;
+
+use itertools::Itertools;
+
+fn main() {
+    let mut data: Vec<_> = std::fs::read_to_string("input.txt")
+        .unwrap()
+        .lines()
+        .map(Neighbors::parse)
+        .collect();
+
+    part1(&data);
+
+    let persons: HashSet<_> = data.iter().map(|p| p.persons.0.clone()).collect();
+    for p in &persons {
+        data.push(Neighbors::new(("me".to_string(), p.to_string()), 0));
+        data.push(Neighbors::new((p.to_string(), "me".to_string()), 0));
+    }
+
+    part1(&data);
+}
+
+fn part1(data: &[Neighbors]) {
+    let persons: HashSet<_> = data.iter().map(|p| p.persons.0.clone()).collect();
+
+    let result = persons
+        .iter()
+        .permutations(persons.len())
+        .map(|order| calculate_happiness(&order, data))
+        .max()
+        .unwrap();
+
+    println!("{result}");
+}
+
+fn calculate_happiness(order: &[&String], neighbors: &[Neighbors]) -> i64 {
+    let mut result = 0;
+
+    let mut order_wrapped = order.to_vec();
+    order_wrapped.push(order[0]);
+
+    for (a, b) in order_wrapped.iter().tuple_windows() {
+        result += neighbors
+            .iter()
+            .filter(|n| {
+                n.persons == (a.to_string(), b.to_string())
+                    || n.persons == (b.to_string(), a.to_string())
+            })
+            .map(|p| p.happiness)
+            .sum::<i64>();
+    }
+
+    result
+}
+
+#[derive(Debug)]
+struct Neighbors {
+    pub persons: (String, String),
+    pub happiness: i64,
+}
+
+impl Neighbors {
+    fn new(persons: (String, String), happiness: i64) -> Self {
+        Self { persons, happiness }
+    }
+
+    fn parse(s: &str) -> Self {
+        let mut parts = s.split_whitespace();
+
+        let a = parts.next().unwrap().to_string();
+        let mut b = parts.next_back().unwrap().to_string();
+        b = b.chars().take(b.len() - 1).collect();
+
+        let lose_gain = parts.nth(1).unwrap();
+
+        let sign = if lose_gain == "gain" { 1 } else { -1 };
+        let amount: i64 = parts.next().unwrap().parse().unwrap();
+
+        let happiness = amount * sign;
+
+        Self::new((a, b), happiness)
+    }
+}