y2015d18

y2015/src/bin/d15.rs

@@ -14,8 +14,8 @@ fn part1() {
 }
 
 fn part2() {
-    let root = env!("CARGO_MANIFEST_DIR");
-    let content = fs::read_to_string(format!("{root}/resources/15_input.txt")).unwrap();
+    //let root = env!("CARGO_MANIFEST_DIR");
+    //let content = fs::read_to_string(format!("{root}/resources/15_input.txt")).unwrap();
     // change comments in part1
     //println!("{}", d15::process_part2(&content));
 }

y2015/src/bin/d18.rs

@@ -10,11 +10,11 @@ fn main() {
 fn part1() {
     let root = env!("CARGO_MANIFEST_DIR");
     let content = fs::read_to_string(format!("{root}/resources/18_input.txt")).unwrap();
-    println!("{}", d18::process_part1(&content));
+    println!("{}", d18::process_part1(&content, 100));
 }
 
 fn part2() {
     let root = env!("CARGO_MANIFEST_DIR");
     let content = fs::read_to_string(format!("{root}/resources/18_input.txt")).unwrap();
-    println!("{}", d18::process_part2(&content));
+    println!("{}", d18::process_part2(&content, 100));
 }

y2015/src/days/d18.rs

@@ -1,26 +1,179 @@
-pub fn process_part1(input: &str) -> i32 {
-    0
+use core::panic;
+
+pub fn process_part1(input: &str, steps: u32) -> i32 {
+    let mut grid = input
+        .lines()
+        .map(|line| line.chars().map(Light::from).collect::<Vec<Light>>())
+        .collect::<Vec<Vec<Light>>>();
+    let height = grid.len();
+    let width = grid[0].len();
+    let mut new_grid = vec![vec![Light::Off; width]; height];
+    for _step in 0..steps {
+        for (y, grid_line) in grid.iter().enumerate() {
+            for (x, light) in grid_line.iter().enumerate() {
+                let neighbors = Light::get_neighbors(grid.clone(), (x, y));
+                new_grid[y][x] = light.new_state(neighbors);
+            }
+        }
+        grid = new_grid.clone();
+    }
+    grid.iter()
+        .map(|line| {
+            line.iter()
+                .map(|&light| if light == Light::On { 1 } else { 0 })
+                .sum::<i32>()
+        })
+        .sum()
 }
 
-pub fn process_part2(input: &str) -> i32 {
-    0
+pub fn process_part2(input: &str, steps: u32) -> i32 {
+    let mut grid = input
+        .lines()
+        .map(|line| line.chars().map(Light::from).collect::<Vec<Light>>())
+        .collect::<Vec<Vec<Light>>>();
+    let height = grid.len();
+    let width = grid[0].len();
+    let corners = vec![
+        (0, 0),
+        (width - 1, 0),
+        (0, height - 1),
+        (width - 1, height - 1),
+    ];
+    for (corner_x, corner_y) in corners.clone() {
+        grid[corner_y][corner_x] = Light::On;
+    }
+    let mut new_grid = vec![vec![Light::Off; width]; height];
+    for _step in 0..steps {
+        for (y, grid_line) in grid.iter().enumerate() {
+            for (x, light) in grid_line.iter().enumerate() {
+                let neighbors = Light::get_neighbors(grid.clone(), (x, y));
+                new_grid[y][x] = light.new_state(neighbors);
+            }
+        }
+        grid = new_grid.clone();
+        for (corner_x, corner_y) in corners.clone() {
+            grid[corner_y][corner_x] = Light::On;
+        }
+    }
+    grid.iter()
+        .map(|line| {
+            line.iter()
+                .map(|&light| if light == Light::On { 1 } else { 0 })
+                .sum::<i32>()
+        })
+        .sum()
+}
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum Light {
+    On,
+    Off,
+}
+
+impl Light {
+    fn new_state(self, neighbors: Vec<Light>) -> Self {
+        let mut light = self;
+        match self {
+            Light::On => {
+                if ![2, 3].contains(&Self::count_on(neighbors)) {
+                    light = Light::Off;
+                }
+            }
+            Light::Off => {
+                if Self::count_on(neighbors) == 3 {
+                    light = Light::On;
+                }
+            }
+        };
+        light
+    }
+
+    fn count_on(neighbors: Vec<Light>) -> u32 {
+        neighbors
+            .iter()
+            .map(|&light| if light == Light::On { 1 } else { 0 })
+            .sum()
+    }
+
+    fn get_neighbors(grid: Vec<Vec<Light>>, coords: (usize, usize)) -> Vec<Light> {
+        let relative_coords = vec![
+            (-1, -1),
+            (0, -1),
+            (1, -1),
+            (-1, 0),
+            (1, 0),
+            (-1, 1),
+            (0, 1),
+            (1, 1),
+        ];
+        let height = grid.len();
+        let width = grid[0].len();
+        let (x, y) = coords;
+        let mut neighbors = Vec::new();
+        for (relative_x, relative_y) in relative_coords {
+            let neighbor_x = x.checked_add_signed(relative_x);
+            if neighbor_x.is_none() {
+                continue;
+            }
+            let neighbor_x = neighbor_x.unwrap();
+            let neighbor_y = y.checked_add_signed(relative_y);
+            if neighbor_y.is_none() {
+                continue;
+            }
+            let neighbor_y = neighbor_y.unwrap();
+            if neighbor_x >= width || neighbor_y >= height {
+                continue;
+            }
+            neighbors.push(grid[neighbor_y][neighbor_x]);
+        }
+        neighbors
+    }
+}
+
+impl From<char> for Light {
+    fn from(value: char) -> Self {
+        match value {
+            '#' => Light::On,
+            '.' => Light::Off,
+            _ => panic!("Wrong character"),
+        }
+    }
+}
+
+#[allow(unused)]
+fn print_grid(grid: Vec<Vec<Light>>) {
+    grid.iter().for_each(|line| {
+        line.iter().for_each(|&light| {
+            if light == Light::On {
+                print!("#");
+            } else {
+                print!(".");
+            }
+        });
+        println!();
+    });
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
-    const INPUT: &str = "{{EXAMPLE}}";
+    const INPUT: &str = ".#.#.#
+...##.
+#....#
+..#...
+#.#..#
+####..";
 
     #[test]
     fn part1() {
-        let result = process_part1(INPUT);
-        assert_eq!(result, 0);
+        let result = process_part1(INPUT, 4);
+        assert_eq!(result, 4);
     }
 
     #[test]
     fn part2() {
-        let result = process_part2(INPUT);
-        assert_eq!(result, 0);
+        let result = process_part2(INPUT, 5);
+        assert_eq!(result, 17);
     }
 }

y2015/src/days/mod.rs

@@ -5,6 +5,9 @@ pub mod d12;
 pub mod d13;
 pub mod d14;
 pub mod d15;
+pub mod d16;
+pub mod d17;
+pub mod d18;
 pub mod d2;
 pub mod d3;
 pub mod d4;
@@ -13,13 +16,3 @@ pub mod d6;
 pub mod d7;
 pub mod d8;
 pub mod d9;
-
-pub mod d16;
-
-pub mod d17;
-
-pub mod d18;
-
-pub mod d18;
-
-pub mod d18;