day5: complete solution

5/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day5"
+version = "0.1.0"

5/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day5"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

5/src/main.rs

@@ -0,0 +1,230 @@
+use std::fmt::Debug;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Lines};
+use std::time::{Duration, Instant};
+
+// BOILERPLATE
+type InputIter = Lines<BufReader<File>>;
+
+pub fn get_input() -> InputIter {
+    let f = File::open("input").unwrap();
+    let br = BufReader::new(f);
+    br.lines()
+}
+
+fn duration_format(duration: Duration) -> String {
+    match duration.as_secs_f64() {
+        x if x > 1.0 => format!("{:.3}s", x),
+        x if x > 0.010 => format!("{:.3}ms", x * 1e3),
+        x => format!("{:.3}us", x * 1e6),
+    }
+}
+
+fn main() {
+    let input = get_input();
+    let start = Instant::now();
+    let ans1 = problem1(input);
+    let duration1 = start.elapsed();
+    println!("Problem 1 solution: {} [{}]", ans1, duration_format(duration1));
+
+    let input = get_input();
+    let start = Instant::now();
+    let ans2 = problem2(input);
+    let duration2 = start.elapsed();
+    println!("Problem 2 solution: {} [{}]", ans2, duration_format(duration2));
+    println!("Total duration: {}", duration_format(duration1 + duration2));
+}
+
+trait Rule: Debug {
+    fn check(&self, pages: &Vec<u64>) -> bool;
+    fn fail_pos(&self, pages: &Vec<u64>) -> Option<(usize, usize)>;
+}
+
+#[derive(Debug)]
+struct BeforeRule {
+    a: u64,
+    b: u64,
+}
+
+impl Rule for BeforeRule {
+    fn check(&self, pages: &Vec<u64>) -> bool {
+        let mut seen_a = false;
+        let mut seen_b = false;
+        for page in pages {
+            if *page == self.a {
+                if seen_b {
+                    return false;
+                }
+                seen_a = true;
+            } else if *page == self.b {
+                if seen_a {
+                    return true;
+                }
+                seen_b = true
+            }
+        }
+        return true;
+    }
+    fn fail_pos(&self, pages: &Vec<u64>) -> Option<(usize, usize)> {
+        let mut a_pos = None;
+        let mut b_pos = None;
+        for (pos, page) in pages.iter().enumerate() {
+            if *page == self.a {
+                if b_pos.is_some() {
+                    return Some((b_pos.unwrap(), pos));
+                }
+                a_pos = Some(pos);
+            } else if *page == self.b {
+                if a_pos.is_some() {
+                    return None;
+                }
+                b_pos = Some(pos);
+            }
+        }
+        None
+    }
+}
+
+impl From<String> for BeforeRule {
+    fn from(line: String) -> BeforeRule {
+        let nums: Vec<_> = line.splitn(2, '|').map(|s| s.parse::<u64>().unwrap()).collect();
+        BeforeRule { a: nums[0], b: nums[1] }
+    }
+}
+
+#[derive(Debug)]
+struct OrderingRules {
+    rules: Vec<Box<dyn Rule>>,
+}
+
+impl OrderingRules {
+    fn check(&self, pages: &Vec<u64>) -> bool {
+        self.rules.iter().all(|p| p.check(pages))
+    }
+    fn fail_pos(&self, pages: &Vec<u64>) -> Option<(usize, usize)> {
+        for rule in &self.rules {
+            let fail_pos = rule.fail_pos(pages);
+            if fail_pos.is_some() {
+                return fail_pos
+            }
+        }
+        None
+    }
+}
+
+// impl<'a, T: Iterator<Item = &'a str>> From<&mut T> for OrderingRules {
+//     fn from(input: &mut T) -> Self {
+//         let mut rules = Vec::new();
+//         for line in input {
+//             rules.push(line.into())
+//         }
+//         Self { rules }
+//     }
+// }
+
+// PROBLEM 1 solution
+
+fn problem1<T: BufRead>(mut input: Lines<T>) -> u64 {
+    let rules = OrderingRules {
+        rules: input
+            .by_ref()
+            .map_while(|l| match l {
+                Ok(line) if line != "" => Some(Box::new(BeforeRule::from(line)) as _),
+                _ => None,
+            })
+            .collect(),
+    };
+    let updates: Vec<Vec<u64>> = input
+        .by_ref()
+        .map(|l| l.unwrap().split(',').map(|n| n.parse::<u64>().unwrap()).collect())
+        .collect();
+
+    let mut res = 0;
+    for update in updates {
+        if rules.check(&update) {
+            res += update[update.len() / 2]
+        }
+    }
+    res
+}
+
+// PROBLEM 2 solution
+fn problem2<T: BufRead>(mut input: Lines<T>) -> u64 {
+    let rules = OrderingRules {
+        rules: input
+            .by_ref()
+            .map_while(|l| match l {
+                Ok(line) if line != "" => Some(Box::new(BeforeRule::from(line)) as _),
+                _ => None,
+            })
+            .collect(),
+    };
+    let updates: Vec<Vec<u64>> = input
+        .by_ref()
+        .map(|l| l.unwrap().split(',').map(|n| n.parse::<u64>().unwrap()).collect())
+        .collect();
+
+    let mut res = 0;
+    for mut update in updates {
+        let mut did_swaps = false;
+        while let Some((a,b)) = rules.fail_pos(&update) {
+            did_swaps = true;
+            update.swap(a, b);
+        }
+        if did_swaps {
+            if !rules.check(&update) {
+                panic!("update still fails after swaps")
+            }
+
+            res += update[update.len() / 2];
+        }
+    }
+    res
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::*;
+    use std::io::Cursor;
+
+    const EXAMPLE: &str = &"47|53
+97|13
+97|61
+97|47
+75|29
+61|13
+75|53
+29|13
+97|29
+53|29
+61|53
+97|53
+61|29
+47|13
+75|47
+97|75
+47|61
+75|61
+47|29
+75|13
+53|13
+
+75,47,61,53,29
+97,61,53,29,13
+75,29,13
+75,97,47,61,53
+61,13,29
+97,13,75,29,47";
+
+    #[test]
+    fn problem1_example() {
+        let c = Cursor::new(EXAMPLE);
+        assert_eq!(problem1(c.lines()), 143);
+    }
+
+    #[test]
+    fn problem2_example() {
+        let c = Cursor::new(EXAMPLE);
+        assert_eq!(problem2(c.lines()), 123);
+    }
+}