day(03): add solution

Signed-off-by: Matej Focko <mfocko@redhat.com>

samples/day03.txt

@@ -0,0 +1,10 @@
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..

src/bin/day03.rs

@@ -0,0 +1,159 @@
+use std::{cmp, collections::HashMap};
+
+use aoc_2023::*;
+
+type Output1 = i32;
+type Output2 = Output1;
+
+struct Day03 {
+    lines: Vec<String>,
+}
+impl Solution<Output1, Output2> for Day03 {
+    fn new<P: AsRef<Path>>(pathname: P) -> Self {
+        Self {
+            lines: file_to_lines(pathname),
+        }
+    }
+
+    fn part_1(&mut self) -> Output1 {
+        let symbols = self
+            .lines
+            .iter()
+            .enumerate()
+            .flat_map(|(y, line)| {
+                line.chars().enumerate().filter_map(move |(x, c)| {
+                    if c != '.' && !c.is_ascii_digit() {
+                        Some(((y + 1, x + 1), c))
+                    } else {
+                        None
+                    }
+                })
+            })
+            .collect::<HashMap<(usize, usize), char>>();
+        let numbers = self
+            .lines
+            .iter()
+            .enumerate()
+            .flat_map(|(y, line)| {
+                let mut nums = vec![];
+
+                let mut start = line.len();
+                let mut num = 0;
+                for (x, c) in line.chars().enumerate() {
+                    if c.is_ascii_digit() {
+                        start = cmp::min(start, x);
+                        num = num * 10 + c.to_digit(10).unwrap() as i32;
+                    } else {
+                        nums.push((y + 1, start + 1, x + 1, num));
+
+                        start = line.len();
+                        num = 0;
+                    }
+                }
+
+                if start != line.len() {
+                    nums.push((y + 1, start + 1, line.len() + 1, num));
+                }
+
+                nums
+            })
+            .collect_vec();
+
+        numbers
+            .iter()
+            .filter_map(|(y, start, x, num)| {
+                if symbols.contains_key(&(*y, start - 1))
+                    || symbols.contains_key(&(*y, *x))
+                    || (*start - 1..=*x).any(|xx| {
+                        symbols.contains_key(&(y - 1, xx)) || symbols.contains_key(&(y + 1, xx))
+                    })
+                {
+                    Some(*num)
+                } else {
+                    None
+                }
+            })
+            .sum()
+    }
+
+    fn part_2(&mut self) -> Output2 {
+        let symbols = self
+            .lines
+            .iter()
+            .enumerate()
+            .flat_map(|(y, line)| {
+                line.chars().enumerate().filter_map(move |(x, c)| {
+                    if c == '*' {
+                        Some(((y + 1, x + 1), c))
+                    } else {
+                        None
+                    }
+                })
+            })
+            .collect::<HashMap<(usize, usize), char>>();
+
+        let mut symbol_counters: HashMap<(usize, usize), Vec<i32>> = HashMap::new();
+
+        let numbers = self
+            .lines
+            .iter()
+            .enumerate()
+            .flat_map(|(y, line)| {
+                let mut nums = vec![];
+
+                let mut start = line.len();
+                let mut num = 0;
+                for (x, c) in line.chars().enumerate() {
+                    if c.is_ascii_digit() {
+                        start = cmp::min(start, x);
+                        num = num * 10 + c.to_digit(10).unwrap() as i32;
+                    } else if start != line.len() {
+                        nums.push((y + 1, start + 1, x + 1, num));
+
+                        start = line.len();
+                        num = 0;
+                    }
+                }
+
+                if start != line.len() {
+                    nums.push((y + 1, start + 1, line.len() + 1, num));
+                }
+
+                nums
+            })
+            .collect_vec();
+
+        numbers.iter().for_each(|(y, start, x, num)| {
+            let mut possible_gears = vec![(*y, start - 1), (*y, *x)];
+
+            (*start - 1..=*x).for_each(|xx: usize| {
+                possible_gears.push((y - 1, xx));
+                possible_gears.push((y + 1, xx));
+            });
+
+            for (y, x) in possible_gears {
+                if symbols.contains_key(&(y, x)) {
+                    symbol_counters.entry((y, x)).or_default().push(*num);
+                    break;
+                }
+            }
+        });
+
+        symbol_counters
+            .values()
+            .filter_map(|nums| {
+                if nums.len() == 2 {
+                    Some(nums.iter().product1::<i32>().unwrap())
+                } else {
+                    None
+                }
+            })
+            .sum()
+    }
+}
+
+fn main() -> Result<()> {
+    Day03::main()
+}
+
+test_sample!(day_03, Day03, 4361, 467835);