From 3b877bf4cc667eb8bcc787d145203600a4dba2d2 Mon Sep 17 00:00:00 2001
From: Prefetch
Date: Sat, 25 Feb 2023 11:41:27 +0100
Subject: Initial commit
---
d18/src/main.rs | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 62 insertions(+)
create mode 100644 d18/src/main.rs
(limited to 'd18/src')
diff --git a/d18/src/main.rs b/d18/src/main.rs
new file mode 100644
index 0000000..a9410f2
--- /dev/null
+++ b/d18/src/main.rs
@@ -0,0 +1,62 @@
+use std::fs;
+
+fn solve_puzzle(first: &str, num_rows: usize) -> usize {
+ let mut total = first.matches('.').count();
+
+ let mut tiles: Vec<char> = first.chars().collect();
+ for _i in 1..num_rows {
+ let mut next = Vec::new();
+
+ for j in 0..tiles.len() {
+ let is_trap;
+
+ // At left wall
+ if j == 0 {
+ is_trap = tiles[j + 1] == '^'; // rule 2 + 4
+ // At right wall
+ } else if j == tiles.len() - 1 {
+ is_trap = tiles[j - 1] == '^'; // rule 1 + 3
+ // Away from the walls
+ } else {
+ is_trap = tiles[j - 1] == '^' && tiles[j + 1] == '.' // rule 1 + 3
+ || tiles[j - 1] == '.' && tiles[j + 1] == '^'; // rule 2 + 4
+ }
+
+ next.push(if is_trap { '^' } else { '.' });
+ }
+
+ tiles = next;
+ total += tiles.iter().filter(|&c| *c == '.').count();
+ }
+
+ total
+}
+
+fn main() {
+ // Read my personal puzzle input
+ let input = fs::read_to_string("input.txt").unwrap();
+ let first = input.trim_end();
+
+ // Part 1 gives 1939 for me
+ println!("Part 1 solution: {}", solve_puzzle(first, 40));
+
+ // Part 2 gives 19999535 for me
+ println!("Part 1 solution: {}", solve_puzzle(first, 400000));
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn part1_example1() {
+ let input = "..^^.";
+ assert_eq!(solve_puzzle(input, 3), 6);
+ }
+
+ #[test]
+ fn part1_example2() {
+ let input = ".^^.^.^^^^";
+ assert_eq!(solve_puzzle(input, 10), 38);
+ }
+}
--
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