Solutions for day14, day18, day19

2016/day18/Cargo.lock

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+[root]
+name = "day18"
+version = "0.1.0"
+

2016/day18/Cargo.toml

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+[package]
+name = "day18"
+version = "0.1.0"
+authors = ["~krowbar"]
+
+[dependencies]

2016/day18/src/main.rs

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+// Trap rules
+// * if 110 or 011, 100, 001
+// where nonexistent sides are considered 0
+
+#[derive(Debug, PartialEq, Clone)]
+enum Tile {
+    Trapped = 1,
+    Safe = 0
+}
+
+type Row = Vec<Tile>;
+type Grid = Vec<Row>;
+
+//Part 1
+
+fn add_row(grid: &mut Grid) {
+    static TRAPS: [[Tile; 3]; 4] =
+    [
+        [Tile::Trapped, Tile::Trapped, Tile::Safe],
+        [Tile::Safe,    Tile::Trapped, Tile::Trapped],
+        [Tile::Trapped, Tile::Safe,    Tile::Safe],
+        [Tile::Safe,    Tile::Safe,    Tile::Trapped],
+    ];
+
+    let last_row = grid.clone().into_iter().last().unwrap();
+    //println!("Last row {:?}", last_row);
+    let mut new_row: Row = vec![];
+
+    for idx in 0..last_row.len() {
+        let mut pre: [Tile; 3] = [Tile::Safe, Tile::Safe, Tile::Safe];
+        if idx > 0 {
+            pre[0] = last_row[idx - 1].clone();
+        }
+        pre[1] = last_row[idx].clone();
+        if idx + 1 < last_row.len() {
+            pre[2] = last_row[idx + 1].clone();
+        }
+        if TRAPS.contains(&pre) {
+            new_row.push(Tile::Trapped);
+        } else {
+            new_row.push(Tile::Safe);
+        }
+    }
+    //println!("New row: {:?}", new_row);
+
+    grid.push(new_row);
+}
+
+fn create_grid(rows: usize) -> Grid {
+    let first_row: Row =
+        String::from(".^..^....^....^^.^^.^.^^.^.....^.^..^...^^^^^^.^^^^.^.^^^^^^^.^^^^^..^.^^^.^^..^.^^.^....^.^...^^.^.")
+        .chars().map(|c| {
+            match c {
+                '^' => Tile::Trapped,
+                 _  => Tile::Safe,
+            }
+        }).collect::<Row>();
+    let mut grid: Grid = vec![first_row];
+    while grid.len() < rows {
+        add_row(&mut grid);
+    }
+    grid
+}
+
+
+// Part 2
+fn step_row(last_row: &mut Row) -> i64 {
+    static TRAPS: [[Tile; 3]; 4] =
+    [
+        [Tile::Trapped, Tile::Trapped, Tile::Safe],
+        [Tile::Safe,    Tile::Trapped, Tile::Trapped],
+        [Tile::Trapped, Tile::Safe,    Tile::Safe],
+        [Tile::Safe,    Tile::Safe,    Tile::Trapped],
+    ];
+
+    let mut new_row: Row = vec![];
+    let mut safe_tiles = 0;
+    for idx in 0..last_row.len() {
+        let mut pre: [Tile; 3] = [Tile::Safe, Tile::Safe, Tile::Safe];
+        if idx > 0 {
+            pre[0] = last_row[idx - 1].clone();
+        }
+        pre[1] = last_row[idx].clone();
+        if idx + 1 < last_row.len() {
+            pre[2] = last_row[idx + 1].clone();
+        }
+        if TRAPS.contains(&pre) {
+            new_row.push(Tile::Trapped);
+        } else {
+            new_row.push(Tile::Safe);
+            safe_tiles = safe_tiles + 1;
+        }
+    }
+    *last_row = new_row;
+    safe_tiles
+}
+
+fn main() {
+    let grid = create_grid(40);
+    let total_safe = grid.iter().fold(0, |sum, r| sum + r.iter().filter(|t| **t == Tile::Safe).count());
+    let total_trap = grid.iter().fold(0, |sum, r| sum + r.iter().filter(|t| **t == Tile::Trapped).count());
+    println!("Part 1: There are {} safe tiles and {} traps", total_safe, total_trap);
+
+    //Need to improve the algorithm so it finishes in a sane amount of time
+    let mut row: Row =
+        String::from(".^..^....^....^^.^^.^.^^.^.....^.^..^...^^^^^^.^^^^.^.^^^^^^^.^^^^^..^.^^^.^^..^.^^.^....^.^...^^.^.")
+        .chars().map(|c| {
+            match c {
+                '^' => Tile::Trapped,
+                 _  => Tile::Safe,
+            }
+        }).collect::<Row>();
+    let mut safe_tiles = 48; //from row 1
+    for _ in 0..400000 - 1 {
+        safe_tiles = safe_tiles + step_row(&mut row);
+    }
+    println!("Part 2: There are {} safe tiles", safe_tiles);
+}