day 8

data/examples/08.txt

@@ -0,0 +1,12 @@
+............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............

src/bin/07.rs

@@ -1,4 +1,4 @@
-use std::collections::{HashSet, VecDeque};
+use std::collections::HashSet;
 
 use itertools::Itertools;
 
@@ -37,7 +37,7 @@ pub fn part_one(input: &str) -> Option<i64> {
     Some(result)
 }
 
-fn solve_equation(equation: &Equation) -> Option<HashSet<VecDeque<char>>> {
+fn solve_equation(equation: &Equation) -> Option<HashSet<Vec<char>>> {
     let mut solutions = HashSet::new();
     if equation.numbers.len() == 2 {
         if equation.numbers[0] + equation.numbers[1] == equation.target {
@@ -68,7 +68,7 @@ fn solve_equation(equation: &Equation) -> Option<HashSet<VecDeque<char>>> {
         if let Some(sols) = add_smaller_solutions {
             for sol in sols {
                 let mut new_sol = sol.clone();
-                new_sol.push_back('+');
+                new_sol.push('+');
                 solutions.insert(new_sol);
             }
         }
@@ -84,7 +84,7 @@ fn solve_equation(equation: &Equation) -> Option<HashSet<VecDeque<char>>> {
         if let Some(sols) = mult_smaller_solutions {
             for sol in sols {
                 let mut new_sol = sol.clone();
-                new_sol.push_back('*');
+                new_sol.push('*');
                 solutions.insert(new_sol);
             }
         };

src/bin/08.rs

@@ -0,0 +1,126 @@
+use itertools::Itertools;
+use std::collections::{HashMap, HashSet};
+
+advent_of_code::solution!(8);
+
+#[derive(Debug, Eq, Hash, PartialEq, Clone, Copy)]
+struct Position(usize, usize);
+
+pub fn part_one(input: &str) -> Option<usize> {
+    let mut x_max = 0;
+    let mut y_max = 0;
+    let mut antenna_groups = HashMap::new();
+    for (y, row) in input.lines().enumerate() {
+        x_max = row.len() - 1;
+        y_max = y;
+        for (x, el) in row.chars().enumerate() {
+            if el == '.' {
+                continue;
+            }
+            antenna_groups
+                .entry(el)
+                .or_insert(vec![])
+                .push(Position(x, y));
+        }
+    }
+
+    let mut antinodes = HashSet::new();
+    for antenna_positions in antenna_groups.values() {
+        for position_pair in antenna_positions.iter().permutations(2) {
+            if let Some(anode) = get_antinode(position_pair[0], position_pair[1], x_max, y_max) {
+                antinodes.insert(anode);
+            }
+        }
+    }
+
+    Some(antinodes.len())
+}
+
+fn get_antinode(
+    left: &Position,
+    right: &Position,
+    x_bound: usize,
+    y_bound: usize,
+) -> Option<Position> {
+    // Left to Right distance
+    let x_delta_lr: isize = right.0 as isize - left.0 as isize;
+    let y_delta_lr: isize = right.1 as isize - left.1 as isize;
+    let antinode_lr_x = right.0.checked_add_signed(x_delta_lr);
+    let antinode_lr_y = right.1.checked_add_signed(y_delta_lr);
+    if let (Some(x), Some(y)) = (antinode_lr_x, antinode_lr_y) {
+        if x <= x_bound && y <= y_bound {
+            return Some(Position(x, y));
+        }
+    };
+    None
+}
+
+pub fn part_two(input: &str) -> Option<usize> {
+    let mut x_max = 0;
+    let mut y_max = 0;
+    let mut antenna_groups = HashMap::new();
+    for (y, row) in input.lines().enumerate() {
+        x_max = row.len() - 1;
+        y_max = y;
+        for (x, el) in row.chars().enumerate() {
+            if el == '.' {
+                continue;
+            }
+            antenna_groups
+                .entry(el)
+                .or_insert(vec![])
+                .push(Position(x, y));
+        }
+    }
+
+    let mut antinodes = HashSet::new();
+    for antenna_positions in antenna_groups.values() {
+        for position_pair in antenna_positions.iter().permutations(2) {
+            let res = get_antinode_2(*position_pair[0], *position_pair[1], x_max, y_max);
+            antinodes.extend(res);
+        }
+    }
+
+    Some(antinodes.len())
+}
+
+fn get_antinode_2(
+    left: Position,
+    right: Position,
+    x_bound: usize,
+    y_bound: usize,
+) -> Vec<Position> {
+    let mut anodes = vec![left.to_owned(), right.to_owned()];
+    let x_delta: isize = right.0 as isize - left.0 as isize;
+    let y_delta: isize = right.1 as isize - left.1 as isize;
+    let mut antinode_x = right.0.checked_add_signed(x_delta);
+    let mut antinode_y = right.1.checked_add_signed(y_delta);
+    while let (Some(x), Some(y)) = (antinode_x, antinode_y) {
+        if x <= x_bound && y <= y_bound {
+            anodes.push(Position(x, y));
+            antinode_x = x.checked_add_signed(x_delta);
+            antinode_y = y.checked_add_signed(y_delta);
+        } else {
+            break;
+        }
+    }
+
+    anodes
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(14));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(34));
+    }
+}