From 4a8c5580ff22d2e2cb5d9f52514ef4cff856c5f8 Mon Sep 17 00:00:00 2001
From: Bas Dado <bas@orbitgames.nl>
Date: Fri, 11 Dec 2020 22:31:05 +0100
Subject: [PATCH] [TASK] Added some padding to the grid to save some time on
 out-of-bounds checks, but it's still pretty slow

---
 src/day11.rs | 37 ++++++++++++++++---------------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/src/day11.rs b/src/day11.rs
index 473977e..13d7265 100644
--- a/src/day11.rs
+++ b/src/day11.rs
@@ -6,7 +6,7 @@ use crate::day11::GridState::EmptySeat;
 pub fn solve() {
     let lines = util::read_file("input/day11.txt");
 
-    let seats = Seats::parse(&lines);
+    let seats = Seats::parse(&lines, 1);
 
     let part1 = solve_part1(&seats);
 
@@ -25,8 +25,8 @@ fn solve_part1(seats: &Seats) -> usize {
 
     loop {
         let mut changes = false;
-        for y in 0..seats.height {
-            for x in 0..seats.width {
+        for y in 1..seats.height-1 {
+            for x in 1..seats.width-1 {
                 let seat = last_seats.get(&x, &y);
                 if seat != &Floor {
                     let occupied = last_seats.count_occupied_neighbors(&x, &y);
@@ -66,8 +66,8 @@ fn solve_part2(seats: &Seats, visible_chairs: &Vec<Option<Vec<(usize, usize)>>>)
                         changes = true;
                         next_seats.set(&x, &y, FilledSeat);
                     } else if seat == &FilledSeat && occupied >= 5 {
-                        next_seats.set(&x, &y, EmptySeat);
                         changes = true;
+                        next_seats.set(&x, &y, EmptySeat);
                     }
                 }
             }
@@ -94,16 +94,16 @@ impl Seats {
 
     const DIRECTIONS: [(i32, i32); 8] = [(-1, 1), (-1, 0), (-1, -1), (0, -1), (0, 1), (1, 1), (1, 0), (1, -1)];
 
-    fn parse(lines: &Vec<String>) -> Seats {
+    fn parse(lines: &Vec<String>, padding: usize) -> Seats {
 
-        let height = lines.len();
-        let width = lines[0].len();
+        let height = lines.len() + padding * 2;
+        let width = lines[0].len() + padding * 2;
         let mut grid = vec!(GridState::Floor; width * height);
         for y in 0..lines.len() {
             let line = &lines[y];
             let mut line_chars = line.chars();
             for x in 0..lines[0].len() {
-                grid[x + y * width] = GridState::parse(&line_chars.next().unwrap())
+                grid[(x + padding) + (y + padding) * width] = GridState::parse(&line_chars.next().unwrap())
             }
         }
 
@@ -170,20 +170,15 @@ impl Seats {
 
     fn count_occupied_neighbors(&self, x: &usize, y: &usize) -> u8 {
 
-        let x_upper = x == &(self.width - &ONE);
-        let x_lower = x == &0;
-        let y_upper = y == &(self.height - &ONE);
-        let y_lower = y == &0;
-
         return
-            if !x_lower && !y_lower && self.is_occupied(&(x - &ONE), &(y - &ONE)) { 1 } else { 0 } +
-            if !x_lower && self.is_occupied(&(x - &ONE), &y) { 1 } else { 0 } +
-            if !x_lower && !y_upper && self.is_occupied(&(x - &ONE), &(y + ONE)) { 1 } else { 0 } +
-            if !y_lower && self.is_occupied(&x, &(y - ONE)) { 1 } else { 0 } +
-            if !y_upper && self.is_occupied(&x, &(y + ONE)) { 1 } else { 0 } +
-            if !x_upper && !y_lower && self.is_occupied(&(x + ONE), &(y - ONE)) { 1 } else { 0 } +
-            if !x_upper && self.is_occupied(&(x + ONE), &y) { 1 } else { 0 } +
-            if !x_upper && !y_upper && self.is_occupied(&(x + ONE), &(y + ONE)) { 1 } else { 0 }
+            if self.is_occupied(&(x - &ONE), &(y - &ONE)) { 1 } else { 0 } +
+            if self.is_occupied(&(x - &ONE), &y) { 1 } else { 0 } +
+            if self.is_occupied(&(x - &ONE), &(y + ONE)) { 1 } else { 0 } +
+            if self.is_occupied(&x, &(y - ONE)) { 1 } else { 0 } +
+            if self.is_occupied(&x, &(y + ONE)) { 1 } else { 0 } +
+            if self.is_occupied(&(x + ONE), &(y - ONE)) { 1 } else { 0 } +
+            if self.is_occupied(&(x + ONE), &y) { 1 } else { 0 } +
+            if self.is_occupied(&(x + ONE), &(y + ONE)) { 1 } else { 0 }
 
     }