feat: day 5

src/bin/05.rs

@@ -0,0 +1,164 @@
+advent_of_code::solution!(5);
+
+#[derive(Debug)]
+struct Rules {
+    rules: Vec<(u32, u32)>
+}
+
+impl From<&[&str]> for Rules {
+    fn from(lines: &[&str]) -> Self {
+        let mut rules: Vec<(u32, u32)> = lines
+            .into_iter()
+            .map(
+                |line| {
+                    let pages = line
+                        .split("|")
+                        .map(|page| page.parse::<u32>().expect("invalid numeric in rules"))
+                        .collect::<Vec<u32>>();
+                    match pages.as_slice() {
+                        [a, b] => (*a, *b),
+                        _ => panic!("invalid input: invalid rule"),
+                    }
+                }
+            )
+            .collect();
+        rules.sort();
+        Self { rules }
+    }
+}
+
+impl Rules {
+    fn pages_after(&self, page: u32) -> Vec::<u32> {
+        self
+            .rules
+            .clone()
+            .into_iter()
+            .filter_map(|r| match r {
+                (p1, p2) if p1 == page => Some(p2),
+                _ => None
+            })
+            .collect()
+    }
+
+    fn pages_before(&self, page: u32) -> Vec::<u32> {
+        self
+            .rules
+            .clone()
+            .into_iter()
+            .filter_map(|r| match r {
+                (p1, p2) if p2 == page => Some(p1),
+                _ => None
+            })
+            .collect()
+    }
+
+    fn get_correct_pages_order(&self, pages: Vec<u32>) -> Vec<u32> {
+        let mut pages_with_order: Vec<(u32, Vec<u32>, Vec<u32>)> = pages
+            .clone()
+            .into_iter()
+            .map(|p|
+                (
+                    p,
+                    self.pages_before(p).into_iter().filter(|pp| pages.contains(pp)).collect(),
+                    self.pages_after(p).into_iter().filter(|pp| pages.contains(pp)).collect(),
+                )
+            )
+            .collect();
+        pages_with_order.sort_by_key(
+            |(p, before, after)| (before.len(), after.len())
+        );
+        pages_with_order.into_iter().map(|(p, _, _)| p).collect()
+    }
+}
+
+#[derive(Debug)]
+struct ImpressionOrder {
+    pages: Vec<u32>
+}
+
+impl ImpressionOrder {
+    fn middle_page(&self) -> Option<u32> {
+        let length = self.pages.len();
+        if length % 2 == 0 {
+            None
+        } else {
+            Some(self.pages[ (length / 2) as usize ])
+        }
+    }
+
+    fn fix_order(&self, rules: &Rules) -> Self {
+        Self {
+            pages: rules.get_correct_pages_order(self.pages.clone())
+        }
+    }
+    
+    fn is_valid(&self, rules: &Rules) -> bool {
+        let mut invalid_pages: Vec<u32> = Vec::new();
+        for p in self.pages.clone() {
+            if invalid_pages.contains(&p) {
+                return false;
+            }
+            invalid_pages.extend(rules.pages_before(p));
+        }
+        true
+    }
+}
+
+impl TryFrom<&&str> for ImpressionOrder {
+    type Error = ();
+    fn try_from(line: &&str) -> Result<Self, Self::Error> {
+        let pages = line.split(",").flat_map(|page| page.parse::<u32>()).collect::<Vec<u32>>();
+        Ok(Self { pages })
+    }
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let input = input
+        .lines()
+        .collect::<Vec<&str>>();
+    let input = input
+        .split(|s|s.is_empty())
+        .collect::<Vec<&[&str]>>();
+
+    let rules: Rules = input[0].into();
+    input[1]
+        .into_iter()
+        .flat_map(ImpressionOrder::try_from)
+        .filter_map(|o| if o.is_valid(&rules) { o.middle_page() } else { None })
+        .sum::<u32>()
+        .into()
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let input = input
+        .lines()
+        .collect::<Vec<&str>>();
+    let input = input
+        .split(|s|s.is_empty())
+        .collect::<Vec<&[&str]>>();
+
+    let rules: Rules = input[0].into();
+    input[1]
+        .into_iter()
+        .flat_map(ImpressionOrder::try_from)
+        .filter_map(|o| if !o.is_valid(&rules) { o.fix_order(&rules).middle_page() } else { None })
+        .sum::<u32>()
+        .into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(143));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(123));
+    }
+}