2018: day03: part2

aoc2018/src/day03.rs

@@ -1,4 +1,5 @@
 use std::collections::HashMap;
+use std::collections::HashSet;
 use std::fmt;
 
 use super::Result;
@@ -7,6 +8,7 @@ const INPUT: &str = include_str!("../input/day03.txt");
 
 pub fn run() -> Result<()> {
     println!("part 1: {}", part1(INPUT)?);
+    println!("part 2: {}", part2(INPUT)?);
 
     Ok(())
 }
@@ -109,21 +111,63 @@ fn part1(input: &str) -> Result<u64> {
     Ok(res)
 }
 
+fn part2(input: &str) -> Result<usize> {
+    let mut map: HashMap<(usize, usize), Vec<usize>> = HashMap::default();
+    let mut set = HashSet::new();
+
+    for line in input.lines() {
+        let claim = parse(line).ok_or(ParseError::new(line))?;
+        set.insert(claim.id);
+
+        for i in 0..claim.width {
+            for j in 0..claim.height {
+                let x = claim.x + i;
+                let y = claim.y + j;
+
+                // add tissue patch at coordinates (x, y)
+                let entry = map.entry((x, y)).or_default();
+                entry.push(claim.id);
+
+                // if overlap, remove claims from possible solutions
+                if entry.len() > 1 {
+                    for id in entry {
+                        set.remove(id);
+                    }
+                }
+            }
+        }
+    }
+
+    assert!(!set.is_empty());
+    Ok(set.into_iter().next().unwrap())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
-    #[test]
+    const PROVIDED: &str = "#1 @ 1,3: 4x4
-    fn part1_provided() {
-        let input = "#1 @ 1,3: 4x4
 #2 @ 3,1: 4x4
 #3 @ 5,5: 2x2
 ";
-        assert_eq!(part1(input).unwrap(), 4);
+
+    #[test]
+    fn part1_provided() {
+        assert_eq!(part1(PROVIDED).unwrap(), 4);
     }
 
     #[test]
     fn part1_real() {
         assert_eq!(part1(INPUT).unwrap(), 114946);
     }
+
+    #[test]
+    fn part2_provided() {
+        assert_eq!(part2(PROVIDED).unwrap(), 3);
+    }
+
+    #[test]
+    fn part2_real() {
+        assert_eq!(part2(INPUT).unwrap(), 877);
+    }
 }

aoc2018/src/main.rs

@@ -2,18 +2,29 @@ use std::env;
 
 use aoc2018::day01;
 use aoc2018::day02;
+use aoc2018::day03;
+
 use aoc2018::Result;
 
 fn main() -> Result<()> {
-    let days = [day01::run, day02::run];
+    let days: &[fn() -> Result<()>] = &[day01::run, day02::run, day03::run];
 
     let mut args = env::args();
     args.next();
 
-    let day = args
+    match args.next() {
-        .next()
+        Some(arg) => {
-        .expect("Please provide a day to launch")
+            let day: usize = arg.parse().expect("Please provide a day number");
-        .parse::<usize>()?;
+            days[day - 1]().expect("error running day specified");
-
+        }
-    days[day - 1]()
+        None => {
+            for (i, day) in days.iter().enumerate() {
+                println!("day{}: ", i);
+                day().expect(&format!("error running day {}", i));
+                println!();
+            }
+        }
+    }
+
+    Ok(())
 }