part 2

src/day3.rs

@@ -8,7 +8,7 @@ pub fn run() {
     let input = fs::read_to_string("./inputs/day3.txt").expect("Could not read file");
 
     println!("\tPart 1: {}", part1(&input));
-    // println!("\tPart 2: {}", part2(&input));
+    println!("\tPart 2: {}", part2(&input));
 }
 
 fn part1(schematic: &str) -> usize {
@@ -46,7 +46,46 @@ fn part1(schematic: &str) -> usize {
     sum_of_parts
 }
 
-// fn part2(calibration_input: &str) -> usize {}
+fn part2(schematic: &str) -> usize {
+    let mut sum_of_parts = 0;
+    let padded_schematic = format!(".\n{schematic}\n.");
+    let number_re = Regex::new(r"\d+").unwrap();
+    let gear_re = Regex::new(r"\*").unwrap();
+    let windows = padded_schematic
+        .lines()
+        .tuple_windows::<(_, _, _)>()
+        .collect::<Vec<_>>();
+
+    for (top, middle, bottom) in windows {
+        for gear in gear_re.find_iter(middle) {
+            let search_range = std::ops::Range {
+                start: gear.range().end.saturating_sub(1),
+                end: gear.range().end + 1,
+            };
+
+            let mut numbers = vec![];
+            for row in [top, middle, bottom] {
+                for num_match in number_re.find_iter(row) {
+                    numbers.push(num_match);
+                }
+            }
+
+            let mut geared_numbers = vec![];
+            for number in numbers {
+                if std::cmp::max(number.range().start + 1, search_range.start)
+                    <= std::cmp::min(number.range().end, search_range.end)
+                {
+                    geared_numbers.push(number.as_str().parse::<usize>().unwrap())
+                }
+            }
+
+            if geared_numbers.len() == 2 {
+                sum_of_parts += geared_numbers[0] * geared_numbers[1];
+            }
+        }
+    }
+    sum_of_parts
+}
 
 #[cfg(test)]
 mod tests {
@@ -68,16 +107,19 @@ mod tests {
         assert_eq!(part1(input), 4361);
     }
 
-    //     #[test]
-    //     fn test_2() {
-    //         let input = "two1nine
-    // eightwothree
-    // abcone2threexyz
-    // xtwone3four
-    // 4nineeightseven2
-    // zoneight234
-    // 7pqrstsixteen";
+    #[test]
+    fn test_2() {
+        let input = "467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..";
 
-    //         assert_eq!(part2(input), 281);
-    //     }
+        assert_eq!(part2(input), 467835);
+    }
 }