Day 6

2 files changed, 46 insertions, 2 deletions

diff --git a/2018/src/day6.rs b/2018/src/day6.rs
new file mode 100644
index 0000000..58fa733
--- /dev/null
+++ b/2018/src/day6.rs
@@ -0,0 +1,42 @@
+use std::io;
+use std::io::BufRead;
+
+const W: i32 = 800;
+
+fn dist(a: (i32, i32), b: (i32, i32)) -> i32 {
+    (b.0 - a.0).abs() + (b.1 - a.1).abs()
+}
+
+pub fn main<T: BufRead>(reader: T) -> io::Result<(String, String)> {
+    let pts: Vec<(i32, i32)> = reader.lines().map(|l| l.unwrap()).map(|line| {
+        let mut spl = line.split(", ").map(|s| s.parse().unwrap());
+        let x = spl.next().unwrap();
+        let y = spl.next().unwrap();
+        (x, y)
+    }).collect();
+
+    let mut borderpts = vec![false; pts.len()];
+    let mut size = vec![0; pts.len()];
+    let mut nsafe = 0;
+
+    for y in -W..W+1 {
+        for x in -W..W+1 {
+            let closest = (0..pts.len()).min_by_key(|&i| dist(pts[i], (x, y))).unwrap();
+            if x == -W || x == W || y == -W || y == W {
+                borderpts[closest] = true;
+            } else {
+                size[closest] += 1;
+            }
+
+            let distsum: i32 = pts.iter().map(|&p| dist(p, (x, y))).sum();
+            if distsum < 10000 {
+                nsafe += 1;
+            }
+        }
+    }
+
+    let part1 = size[(0..pts.len()).max_by_key(|&i| if borderpts[i] { -1 } else { size[i] }).unwrap()].to_string();
+    let part2 = nsafe.to_string();
+
+    Ok((part1, part2))
+}
diff --git a/2018/src/main.rs b/2018/src/main.rs
index f9098eb..c35e142 100644
--- a/2018/src/main.rs
+++ b/2018/src/main.rs
@@ -14,8 +14,9 @@ mod day2;
 mod day3;
 mod day4;
 mod day5;
+mod day6;
 
-static NUM_DAYS: i32 = 5;
+static NUM_DAYS: i32 = 6;
 
 fn day_switch<T: BufRead>(day: i32, reader: T) -> io::Result<(String, String)> {
     match day {
@@ -24,6 +25,7 @@ fn day_switch<T: BufRead>(day: i32, reader: T) -> io::Result<(String, String)> {
         3 => day3::main(reader),
         4 => day4::main(reader),
         5 => day5::main(reader),
+        6 => day6::main(reader),
         _ => Err(Error::new(ErrorKind::Other, "Invalid day"))
     }
 }
@@ -89,7 +91,7 @@ fn run_all_days(opts: &Options) -> io::Result<()> {
         assert!(!opts.use_stdin);
         benchmark_all_days()
     } else {
-        for day in 1..6 {
+        for day in 1..NUM_DAYS + 1 {
             run_day(day, &opts)?;
         }
         Ok(())