Optimise day 17 a bit

1 files changed, 15 insertions, 10 deletions

diff --git a/2018/src/day17.rs b/2018/src/day17.rs
index 3730e60..f920421 100644
--- a/2018/src/day17.rs
+++ b/2018/src/day17.rs
@@ -174,8 +174,9 @@ fn apply_patterns(grid: &mut Grid, (x, y): (i32, i32)) -> Vec<(i32, i32)> {
     }
 
     for dx in &[-1, 1] {
-        // WP···PW  ->  W~···~W
-        //  W···W        W···W
+        // if dx = 1:
+        // WP?···?W  ->  W~···~W   where ? in {P, .}
+        //  W····W        W···W
         if grid.get(x, y).produces() && grid.get(x, y+1).is_wall() && grid.get(x-dx, y).is_wall() {
             let mut x2 = x + dx;
             let make_still;
@@ -186,20 +187,20 @@ fn apply_patterns(grid: &mut Grid, (x, y): (i32, i32)) -> Vec<(i32, i32)> {
                     break;
                 }
 
-                if !(grid.get(x2, y).produces() && grid.get(x2, y+1).is_wall()) {
+                if (grid.get(x2, y).produces() || grid.get(x2, y) == Cell::Sand) && grid.get(x2, y+1).is_wall() {
+                    x2 += dx;
+                } else {
                     make_still = false;
                     break;
                 }
-
-                x2 += dx;
             }
 
             if make_still {
-                x2 = x;
-                while !grid.get(x2, y).is_wall() {
-                    grid.set(x2, y, Cell::Still);
-                    res.push((x2, y-1));
-                    x2 += dx;
+                let mut x3 = x;
+                while x3 != x2 {
+                    grid.set(x3, y, Cell::Still);
+                    res.push((x3, y-1));
+                    x3 += dx;
                 }
             }
         }
@@ -253,6 +254,10 @@ pub fn main<T: BufRead>(reader: T) -> io::Result<(String, String)> {
         // inqueue.remove(&(x, y));
         // let pos = (x, y);
 
+        if grid.get(pos.0, pos.1) == Cell::Still {
+            continue;
+        }
+
         for &(x, y) in apply_patterns(&mut grid, pos).iter().filter(|&&(x, y)| grid.inrange(x, y)) {
             let p = (-y, x);
             // let p = (x, y);