2023-16: Implement part two

src/year_2023/day_16_the_floor_will_be_lava/mod.rs

@@ -1,5 +1,5 @@
 pub mod part_one;
-// pub mod part_two;
+pub mod part_two;
 pub mod common;
 
 use crate::utils::solution::Solution;
@@ -19,7 +19,7 @@ impl Solution for DaySolution {
     }
 
     fn part_two(&self) -> String {
-        // input_reader::read_input_file(self.input_path(), part_two::part_two)
-        String::from("Not implemented")
+        input_reader::read_input_file(self.input_path(), part_two::part_two)
+        // String::from("Not implemented")
     }
 }

src/year_2023/day_16_the_floor_will_be_lava/part_two.rs

@@ -0,0 +1,132 @@
+use std::collections::HashSet;
+
+use super::common::{Contraption, Direction};
+
+pub fn part_two(input_lines: Vec<String>) -> String {
+
+    let mut contraption: Vec<Vec<Contraption>> = Vec::new();
+    for line in input_lines {
+        let mut row: Vec<Contraption> = Vec::new();
+        for c in line.chars() {
+            match c {
+                '.' => row.push(Contraption::Empty),
+                '\\' => row.push(Contraption::MirrorLeft),
+                '/' => row.push(Contraption::MirrorRight),
+                '|' => row.push(Contraption::SplitterVert),
+                '-' => row.push(Contraption::SplitterHoriz),
+                _ => panic!("Unknown character: {}", c),
+            }
+        }
+        contraption.push(row);
+    }
+
+    let mut max_energy = 0;
+
+    let mut start_stack: Vec<(i32, i32, Direction)> = Vec::new();
+
+    for i in 0..contraption.len() {
+        start_stack.push((i as i32, 0, Direction::Right));     
+        start_stack.push((i as i32,  contraption[0].len() as i32 - 1, Direction::Left));   
+    }
+
+    for j in 0..contraption[0].len() {
+        start_stack.push((0, j as i32, Direction::Down));
+        start_stack.push((contraption.len() as i32 - 1, j as i32, Direction::Up));
+
+    }
+
+    while let Some((start_i, start_j, start_direction)) = start_stack.pop() {
+
+        // print_contraption(&contraption);
+        let mut energized: Vec<Vec<bool>> = vec![vec![false; contraption[0].len()]; contraption.len()];
+        let mut memory: HashSet<(i32, i32, Direction)> = HashSet::new();
+        let mut stack: Vec<(i32, i32, Direction)> = Vec::new();
+        stack.push((start_i, start_j, start_direction));
+
+        while let Some((i, j, direction)) = stack.pop() {
+
+            if i >= contraption[0].len() as i32 || j >= contraption.len() as i32 || i < 0 || j < 0 {
+                continue;
+            }
+
+            if memory.contains(&(i, j, direction))  {
+                continue;
+            } else {
+                memory.insert((i, j, direction));
+            }
+
+            energized[i as usize][j as usize] = true;
+
+            let tile = &contraption[i as usize][j as usize];
+            // println!("{} {}: {:?} - {:?}", i, j, direction, tile);
+
+            match (tile, direction) {
+                (Contraption::Empty, Direction::Right) => {
+                    stack.push((i, j+1, Direction::Right));
+                },
+                (Contraption::Empty, Direction::Left) => {
+                    stack.push((i, j-1, Direction::Left));
+                },
+                (Contraption::Empty, Direction::Up) => {
+                    stack.push((i-1, j, Direction::Up));
+                },
+                (Contraption::Empty, Direction::Down) => {
+                    stack.push((i+1, j, Direction::Down));
+                },
+                (Contraption::MirrorLeft, Direction::Right) => {
+                    stack.push((i+1, j, Direction::Down));
+                }
+                (Contraption::MirrorLeft, Direction::Left) => {
+                    stack.push((i-1, j, Direction::Up));
+                },
+                (Contraption::MirrorLeft, Direction::Up) => {
+                    stack.push((i, j-1, Direction::Left));
+                },
+                (Contraption::MirrorLeft, Direction::Down) => {
+                    stack.push((i, j+1, Direction::Right));
+                },
+                (Contraption::MirrorRight, Direction::Right) => {
+                    stack.push((i-1, j, Direction::Up));
+                },
+                (Contraption::MirrorRight, Direction::Left) => {
+                    stack.push((i+1, j, Direction::Down));
+                },
+                (Contraption::MirrorRight, Direction::Up) => {
+                    stack.push((i, j+1, Direction::Right));
+                },
+                (Contraption::MirrorRight, Direction::Down) => {
+                    stack.push((i, j-1, Direction::Left));
+                },
+                (Contraption::SplitterVert, Direction::Right | Direction::Left) => {
+                    stack.push((i-1, j, Direction::Up));
+                    stack.push((i+1, j, Direction::Down));
+                },
+                (Contraption::SplitterVert, Direction::Down) => {
+                    stack.push((i+1, j, Direction::Down));
+                },
+                (Contraption::SplitterVert, Direction::Up) => {
+                    stack.push((i-1, j, Direction::Up));
+                },
+                (Contraption::SplitterHoriz, Direction::Up | Direction::Down) => {
+                    stack.push((i, j-1, Direction::Left));
+                    stack.push((i, j+1, Direction::Right));
+                },
+                (Contraption::SplitterHoriz, Direction::Left) => {
+                    stack.push((i, j-1, Direction::Left));
+                },
+                (Contraption::SplitterHoriz, Direction::Right) => {
+                    stack.push((i, j+1, Direction::Right));
+                }
+            }
+        }
+
+        // print_energized(&energized);
+
+        let energized_count = energized.iter().flatten().filter(|x| **x).count();
+        if energized_count > max_energy {
+            max_energy = energized_count;
+        }
+    }
+
+    max_energy.to_string()
+}