3 files changed, 49 insertions, 1 deletions
diff --git a/2018/input/11.txt b/2018/input/11.txt
new file mode 100644
index 0000000..9b5f360
--- /dev/null
+++ b/2018/input/11.txt
@@ -0,0 +1 @@
+1723
diff --git a/2018/src/day11.rs b/2018/src/day11.rs
new file mode 100644
index 0000000..4503561
--- /dev/null
+++ b/2018/src/day11.rs
@@ -0,0 +1,45 @@
+use std::io;
+use std::io::BufRead;
+use std::ops::Range;
+
+fn power(x: i32, y: i32, serial: i32) -> i32 {
+    (y * (x + 10) + serial) * (x + 10) / 100 % 10 - 5
+}
+
+fn optimise(grid: [[i32; 300]; 300], srange: Range<usize>) -> (usize, usize, usize) {
+    let mut maxval = i32::min_value();
+    let mut maxat = (0, 0, 0);
+    for s in srange {
+        for y in 0..301-s {
+            for x in 0..301-s {
+                let tot = (0..s).map(|dy| (0..s).map(|dx| grid[y+dy][x+dx]).sum::<i32>()).sum();
+
+                if tot > maxval {
+                    maxval = tot;
+                    maxat = (x, y, s);
+                }
+            }
+        }
+    }
+
+    maxat
+}
+
+pub fn main<T: BufRead>(reader: T) -> io::Result<(String, String)> {
+    let serial = reader.lines().next().unwrap().unwrap().parse::<i32>().unwrap();
+
+    let mut grid = [[0; 300]; 300];
+    for y in 0..300 {
+        for x in 0..300 {
+            grid[y][x] = power(x as i32, y as i32, serial);
+        }
+    }
+
+    let maxat = optimise(grid, 3..4);
+    let part1 = format!("{},{}", maxat.0, maxat.1);
+
+    let maxat = optimise(grid, 1..301);
+    let part2 = format!("{},{},{}", maxat.0, maxat.1, maxat.2);
+
+    Ok((part1, part2))
+}
diff --git a/2018/src/main.rs b/2018/src/main.rs
index 3e9756b..e3622a3 100644
--- a/2018/src/main.rs
+++ b/2018/src/main.rs
@@ -15,8 +15,9 @@ mod day7;
 mod day8;
 mod day9;
 mod day10;
+mod day11;
 
-static NUM_DAYS: i32 = 10;
+static NUM_DAYS: i32 = 11;
 
 fn day_switch<T: BufRead>(day: i32, reader: T) -> io::Result<(String, String)> {
     match day {
@@ -30,6 +31,7 @@ fn day_switch<T: BufRead>(day: i32, reader: T) -> io::Result<(String, String)> {
         8 => day8::main(reader),
         9 => day9::main(reader),
         10 => day10::main(reader),
+        11 => day11::main(reader),
         _ => Err(Error::new(ErrorKind::Other, "Invalid day"))
     }
 }