Add day 3

2023/day3/.gitignore

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+/target/

2023/day3/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day3"
+version = "0.1.0"
+dependencies = [
+ "indoc",
+]
+
+[[package]]
+name = "indoc"
+version = "2.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e186cfbae8084e513daff4240b4797e342f988cecda4fb6c939150f96315fd8"

2023/day3/Cargo.toml

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+[package]
+name = "day3"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+indoc = "2.0.4"

2023/day3/src/main.rs

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+use std::cmp::min;
+
+#[derive(Debug)]
+struct Point {
+    x: usize,
+    y: usize,
+}
+
+#[derive(Debug, Eq, PartialEq)]
+struct Number {
+    line: usize,
+    range: (usize, usize),
+}
+
+impl Number {
+    fn value(&self, lines: &[&str]) -> usize {
+        let mut accum: usize = 0;
+        for (i, x) in (self.range.0..=self.range.1).rev().enumerate() {
+            let val = lines[self.line].chars().collect::<Vec<char>>()[x]
+                .to_digit(10)
+                .unwrap() as usize;
+            accum += val * 10_usize.pow(i as u32);
+        }
+        accum
+    }
+
+    fn contains(&self, point: &Point) -> bool {
+        point.y == self.line && point.x >= self.range.0 && point.x <= self.range.1
+    }
+}
+
+fn find_numbers(lines: &[&str]) -> Vec<Number> {
+    let mut numbers: Vec<Number> = vec![];
+
+    for (y, line) in lines.iter().enumerate() {
+        let mut in_number = false;
+        let mut start = 0;
+        for (x, c) in line.chars().enumerate() {
+            if c.is_ascii_digit() {
+                if !in_number {
+                    start = x;
+                    in_number = true;
+                }
+            } else if in_number {
+                let end = x - 1;
+                in_number = false;
+                numbers.push(Number {
+                    line: y,
+                    range: (start, end),
+                })
+            }
+        }
+        if in_number {
+            numbers.push(Number {
+                line: y,
+                range: (start, line.len() - 1),
+            })
+        }
+    }
+
+    numbers
+}
+
+fn part1(input: &str) -> usize {
+    let lines: Vec<&str> = input.lines().collect();
+    let numbers = find_numbers(&lines);
+
+    let mut numbers_with_adjacent_symbol = vec![];
+
+    for number in &numbers {
+        let mut has_adjacent_symbol = false;
+
+        let bounding_box: (Point, Point) = (
+            Point {
+                // this would underflow on the first column
+                x: number.range.0.saturating_sub(1),
+                // this would underflow on the first line
+                y: number.line.saturating_sub(1),
+            },
+            Point {
+                x: min(number.range.1 + 1, lines[number.line].len() - 1),
+                // this would overflow on the last line
+                y: min(number.line + 1, lines.len() - 1),
+            },
+        );
+
+        'outer: for line in lines
+            .iter()
+            .skip(bounding_box.0.y)
+            .take(bounding_box.1.y + 1)
+        {
+            for x in bounding_box.0.x..=bounding_box.1.x {
+                let c = line.chars().collect::<Vec<char>>()[x];
+                if !c.is_ascii_digit() && c != '.' {
+                    has_adjacent_symbol = true;
+                    break 'outer;
+                }
+            }
+        }
+
+        if has_adjacent_symbol {
+            numbers_with_adjacent_symbol.push(number);
+        }
+    }
+
+    let sum: usize = numbers_with_adjacent_symbol
+        .into_iter()
+        .map(|n| n.value(&lines))
+        .sum();
+
+    sum
+}
+
+fn part2(input: &str) -> usize {
+    let mut gears: Vec<Point> = vec![];
+
+    let lines: Vec<&str> = input.lines().collect();
+
+    let numbers = find_numbers(&lines);
+
+    for (y, line) in lines.iter().enumerate() {
+        for (x, c) in line.chars().enumerate() {
+            if c == '*' {
+                gears.push(Point { x, y });
+            }
+        }
+    }
+
+    let mut gear_ratios: Vec<Vec<&Number>> = vec![];
+    for gear in &gears {
+        let mut matching_numbers: Vec<&Number> = vec![];
+        for number in &numbers {
+            for x in gear.x.saturating_sub(1)..=min(gear.x + 1, lines[0].len()) {
+                for y in gear.y.saturating_sub(1)..=min(gear.y + 1, lines.len()) {
+                    let point = Point { x, y };
+                    if number.contains(&point) && !matching_numbers.contains(&number) {
+                        matching_numbers.push(number);
+                    }
+                }
+            }
+        }
+        if matching_numbers.len() >= 2 {
+            gear_ratios.push(matching_numbers);
+        }
+    }
+
+    gear_ratios
+        .into_iter()
+        .map(|gear_numbers| {
+            gear_numbers
+                .into_iter()
+                .map(|n| n.value(&lines))
+                .product::<usize>()
+        })
+        .sum()
+}
+
+fn main() {
+    let input = std::fs::read_to_string("./input").unwrap();
+
+    println!("Part 1 : {}", part1(&input));
+    println!("Part 2 : {}", part2(&input));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+
+    #[test]
+    fn example_01() {
+        let input = indoc! {"
+            467..114..
+            ...*......
+            ..35..633.
+            ......#...
+            617*......
+            .....+.58.
+            ..592.....
+            ......755.
+            ...$.*....
+            .664.598..
+        "};
+
+        assert_eq!(part1(input), 4361);
+    }
+
+    #[test]
+    fn example_02() {
+        let input = indoc! {"
+                467..114..
+                ...*......
+                ..35..633.
+                ......#...
+                617*......
+                .....+.58.
+                ..592.....
+                ......755.
+                ...$.*....
+                .664.598..
+            "};
+
+        assert_eq!(part2(input), 467835);
+    }
+}