1 files changed, 45 insertions, 0 deletions
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))
+}