feat: add day 3 - part 1

day_3/src/lib.rs

@@ -0,0 +1,108 @@
+#[derive(Debug, PartialEq)]
+pub struct NumberPosition {
+    pub index_start: usize,
+    pub index_end: usize,
+    pub value: usize,
+}
+
+pub fn get_numbers_positions_from_line(line: &str) -> Vec<NumberPosition> {
+    let mut result = vec![];
+    let mut number_string = String::from("");
+    let mut index_start = 0;
+    let mut index_end = 0;
+    for (index_character, character) in line.chars().enumerate() {
+        if character.is_ascii_digit() {
+            if number_string.is_empty() {
+                index_start = index_character;
+            }
+            index_end = index_character;
+            number_string += &character.to_string();
+        } else if !number_string.is_empty() {
+            let value: usize = number_string.parse().expect("Should parse as a `usize`");
+            result.push(NumberPosition {
+                index_start,
+                index_end,
+                value,
+            });
+            number_string = String::from("");
+            index_start = 0;
+            index_end = 0;
+        }
+    }
+    if !number_string.is_empty() {
+        let value: usize = number_string.parse().expect("Should parse as a `usize`");
+        result.push(NumberPosition {
+            index_start,
+            index_end,
+            value,
+        });
+    }
+    result
+}
+
+pub fn is_symbol(character: char) -> bool {
+    !character.is_ascii_digit() && character != '.'
+}
+
+pub fn part_1(input: &str) -> usize {
+    let lines = input.lines().collect::<Vec<&str>>();
+    lines
+        .iter()
+        .enumerate()
+        .map(|(index_line, &line)| {
+            get_numbers_positions_from_line(line)
+                .iter()
+                .filter(|&number_position| {
+                    let index_start = number_position.index_start.saturating_sub(1);
+                    let index_end = if number_position.index_end + 1 >= line.len() {
+                        line.len().saturating_sub(1)
+                    } else {
+                        number_position.index_end + 1
+                    };
+
+                    let has_symbol_on_the_left =
+                        line.chars().nth(index_start).is_some_and(is_symbol);
+                    let has_symbol_on_the_right =
+                        line.chars().nth(index_end).is_some_and(is_symbol);
+
+                    let has_symbol_on_the_top = lines
+                        .get(index_line.saturating_sub(1))
+                        .is_some_and(|&line| {
+                            line.get(index_start..=index_end)
+                                .is_some_and(|value| value.chars().any(is_symbol))
+                        });
+
+                    let has_symbol_on_the_bottom = lines.get(index_line + 1).is_some_and(|&line| {
+                        line.get(index_start..=index_end)
+                            .is_some_and(|value| value.chars().any(is_symbol))
+                    });
+
+                    has_symbol_on_the_left
+                        || has_symbol_on_the_right
+                        || has_symbol_on_the_top
+                        || has_symbol_on_the_bottom
+                })
+                .map(|matching_number| matching_number.value)
+                .sum::<usize>()
+        })
+        .sum()
+}
+
+// pub fn part_2(_input: &str) -> usize {
+//     42
+// }
+
+#[cfg(test)]
+mod day_3_tests {
+    use super::*;
+
+    #[test]
+    fn test_part_1_example() {
+        assert_eq!(part_1(include_str!("../input_example_1.txt")), 4361);
+    }
+
+    // #[test]
+    // fn test_part_2_example() {
+    //     assert_eq!(part_2(include_str!("../input_example_1.txt")), 467835);
+    // }
+}

day_3/src/main.rs

@@ -0,0 +1,8 @@
+use day_3::part_1;
+
+fn main() {
+    let input = include_str!("../input.txt");
+    println!("- Day 3: Gear Ratios -");
+    println!("Answer Part 1: {}", part_1(input));
+    // println!("Answer Part 2: {}", part_2(input));
+}