Part 1

2024/rust/src/day10.rs

@@ -0,0 +1,115 @@
+mod prelude;
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(10);
+    show_answers(part1(&input), part2(&input));
+}
+
+fn part1(input: &str) -> usize {
+    println!("{input}");
+    let mut sum = 0;
+    let map: Vec<Vec<u8>> = input
+        .lines()
+        .map(|l| l.bytes().map(|b| b - b'0').collect())
+        .collect();
+    for (y, row) in map.iter().enumerate() {
+        for (x, height) in row.iter().enumerate() {
+            let mut scores = HashSet::new();
+            if *height == 0 {
+                capture_scores(&map, *height, x, y, &mut scores);
+                sum += scores.len();
+            }
+            println!("{x} {y} {height}");
+        }
+    }
+    sum
+}
+
+fn capture_scores(
+    map: &Vec<Vec<u8>>,
+    height: u8,
+    x: usize,
+    y: usize,
+    scores: &mut HashSet<(usize, usize)>,
+) {
+    if height == 9 {
+        scores.insert((x, y));
+        println!("found a 9");
+    }
+    for (nx, ny) in [
+        (x + 1, y),
+        (x.saturating_sub(1), y),
+        (x, y + 1),
+        (x, y.saturating_sub(1)),
+    ] {
+        if nx >= map[0].len() || ny >= map.len() {
+            continue;
+        }
+        let next_height = map[ny][nx];
+        if next_height.saturating_sub(height) == 1 {
+            println!("{height} -> {next_height} at {nx},{ny}");
+            capture_scores(map, next_height, nx, ny, scores)
+        }
+    }
+}
+
+fn part2(input: &str) -> usize {
+    println!("{input}");
+    let mut sum = 0;
+    let map: Vec<Vec<u8>> = input
+        .lines()
+        .map(|l| l.bytes().map(|b| b - b'0').collect())
+        .collect();
+    for (y, row) in map.iter().enumerate() {
+        for (x, height) in row.iter().enumerate() {
+            if *height == 0 {
+                sum += find_paths_to_nines(&map, *height, x, y);
+            }
+            println!("{x} {y} {height}");
+        }
+    }
+    sum
+}
+
+fn find_paths_to_nines(map: &Vec<Vec<u8>>, height: u8, x: usize, y: usize) -> usize {
+    let mut sum = 0;
+    if height == 9 {
+        return 1;
+    }
+    for (nx, ny) in [
+        (x + 1, y),
+        (x.saturating_sub(1), y),
+        (x, y + 1),
+        (x, y.saturating_sub(1)),
+    ] {
+        if nx >= map[0].len() || ny >= map.len() {
+            continue;
+        }
+        let next_height = map[ny][nx];
+        if next_height.saturating_sub(height) == 1 {
+            println!("{height} -> {next_height} at {nx},{ny}");
+            sum += find_paths_to_nines(map, next_height, nx, ny)
+        }
+    }
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = r#"89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732"#;
+        assert_eq!(part1(input), 36);
+        assert_eq!(part2(input), 81);
+    }
+}

2024/rust/src/day11.rs

@@ -0,0 +1,56 @@
+mod prelude;
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(11);
+    show_answers(part1(&input), part2(&input));
+}
+
+fn part1(input: &str) -> usize {
+    stone_blinks(input, 25)
+}
+
+fn stone_blinks(input: &str, count: usize) -> usize {
+    let mut stones: Vec<usize> = input
+        .trim()
+        .split(" ")
+        .map(|s| s.parse().unwrap())
+        .collect();
+    let mut next_stones = vec![];
+    for blink in 0..count {
+        println!("{blink} {}", stones.len());
+        for (_i, s) in stones.iter().enumerate() {
+            // next_stones.push(*s)
+            if *s == 0 {
+                next_stones.push(1);
+                continue;
+            }
+            let ss = s.to_string();
+            if ss.len() % 2 == 0 {
+                let mid = ss.len() / 2;
+                let (s1, s2) = (ss[0..mid].parse().unwrap(), ss[mid..].parse().unwrap());
+                next_stones.push(s1);
+                next_stones.push(s2);
+                continue;
+            }
+            next_stones.push(s * 2024)
+        }
+        stones = next_stones;
+        next_stones = vec![];
+    }
+    stones.len()
+}
+
+fn part2(input: &str) -> usize {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = r#"125 17"#;
+        assert_eq!(part1(input), 55312);
+        assert_eq!(part2(input), 0);
+    }
+}

2024/rust/src/day2.rs

@@ -24,30 +24,29 @@ impl FromStr for Report {
 
 impl Report {
     fn is_safe(&self, skip_index: Option<usize>) -> bool {
-        let mut index_sequence: Box<dyn Iterator<Item = &i64>> = if let Some(i) = skip_index {
-            Box::new(
-                self.levels[0..i]
-                    .iter()
-                    .chain(self.levels[i + 1..self.levels.len()].iter())
-                    .into_iter(),
-            )
+        let mut ordering: Option<Ordering> = None;
+        let skip_index = skip_index.unwrap_or(self.levels.len() + 1);
+        let max = if skip_index < self.levels.len() {
+            self.levels.len() - 2
         } else {
-            Box::new(self.levels.iter())
+            self.levels.len() - 1
         };
-        let a = index_sequence.next().unwrap();
-        let b = index_sequence.next().unwrap();
-        let ordering = a.cmp(b);
-        if ordering == Ordering::Equal {
+
+        for i in 0..max {
+            let mut ai = i;
+            let mut bi = ai + 1;
+            if ai >= skip_index {
+                ai += 1
+            };
+            if bi >= skip_index {
+                bi += 1
+            };
+            let (a, b) = (self.levels[ai], self.levels[bi]);
+            if !Self::safe_level_pair(a, b, &ordering) {
                 return false;
             }
-        if !Self::safe_level_pair(*a, *b, ordering) {
-            return false;
-        }
-        println!("{a} {b} {ordering:?} {skip_index:?}");
-        while let (a, Some(b)) = (b, index_sequence.next()) {
-            println!("{a} {b} {ordering:?}");
-            if !Self::safe_level_pair(*a, *b, ordering) {
-                return false;
+            if ordering == None {
+                ordering = Some(a.cmp(&b))
             }
         }
 
@@ -55,13 +54,25 @@ impl Report {
     }
 
     fn is_safe_with_any_single_level_removed(&self) -> bool {
-        (0..self.levels.len())
-            .into_iter()
-            .any(|i| self.is_safe(Some(i)))
+        for i in 0..self.levels.len() {
+            if self.is_safe(Some(i)) {
+                return true;
+            }
+        }
+        return false;
     }
 
-    fn safe_level_pair(a: i64, b: i64, kind: Ordering) -> bool {
-        kind == a.cmp(&b) && (a - b).abs() <= 3
+    fn safe_level_pair(a: i64, b: i64, kind: &Option<Ordering>) -> bool {
+        if a == b {
+            return false;
+        }
+        if (a - b).abs() > 3 {
+            return false;
+        }
+        if kind.map(|o| o == a.cmp(&b)) == Some(false) {
+            return false;
+        }
+        return true;
     }
 }
 

2024/rust/src/day3.rs

@@ -0,0 +1,130 @@
+mod prelude;
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(3);
+    show_answers(sum_muls(&input), sum_muls_with_do_and_dont(&input));
+}
+
+fn sum_muls(input: &str) -> usize {
+    let mut sum = 0;
+
+    // this string slice will be how we keep track of what is "left" to parse
+    // though it would likely be easier to use an index and slice as needed :shrug:
+    let mut s = &input[..];
+
+    // look for the next valid mul operation
+    while let Some(i) = s.find("mul(") {
+        // re-slice to the remaining string
+        s = &s[i + 4..];
+
+        // variables to contain our operands
+        let mut left: Option<usize> = None;
+        let mut right: Option<usize> = None;
+
+        // variable to contain our currently-parsing token, as we will continue
+        // from here one character at a time
+        let mut token = &s[0..0];
+
+        for c in s.chars() {
+            match c {
+                // any digit simply gets "appended" to our token (in reality, we are just increasing the length of the token slice)
+                '0'..='9' => {
+                    token = &s[0..token.len() + 1];
+                    // the problem indicates that numbers may not be longer than
+                    // 3 digits, so if we encounter one, we break out of this
+                    // loop and head to the next mul operation
+                    if token.len() > 3 {
+                        break;
+                    }
+                }
+
+                // once we hit a comma, we check that we don't already have
+                // a left operand then parse the number (which we can unwrap
+                // since we are assuring we are dealing with digits above,
+                // though we could easily optimize that out with bit of
+                // arithmetic), advance through our string slice, and reset our
+                // currently-parsing token
+                ',' => {
+                    if left.is_some() {
+                        break;
+                    }
+                    left = Some(token.parse().unwrap());
+                    s = &s[token.len() + 1..];
+                    token = &s[0..0];
+                }
+
+                // pretty much the same logic for finding a comma, but for the
+                // right operand
+                ')' => {
+                    if right.is_some() {
+                        break;
+                    }
+                    right = Some(token.parse().unwrap());
+                    s = &s[token.len() + 1..];
+                    token = &s[0..0];
+                }
+                _ => break,
+            }
+        }
+        if let (Some(left), Some(right)) = (left, right) {
+            sum += left * right;
+        }
+    }
+    sum
+}
+
+fn sum_muls_with_do_and_dont(input: &str) -> usize {
+    // the gist of this function is that we look for string segments that are
+    // between do() and don't() operations and only sum_muls for those NOT
+    // between a don't() and do()
+    let mut sum = 0;
+    let mut s = &input[..];
+
+    // since there may be a case where the last do() or don't() is a do(),
+    // we need to know whether or not to parse the "remainder" after we have
+    // processed the last don't() segment which may have ended with a do()
+    let mut mul_rest = true;
+    while let Some(i) = s.find("don't()") {
+        // once we find a don't, we know we want to sum_muls for everything up
+        // to the current position
+        sum += sum_muls(&s[0..i]);
+
+        // then we can advance our slice
+        s = &s[i..];
+        mul_rest = false;
+        if let Some(i) = s.find("do()") {
+            // if we find a do(), set our mul_rest flag appropriately, advance
+            // along the slice, and head to the next iteration (or be done in
+            // the loop)
+            s = &s[i..];
+            mul_rest = true;
+        }
+    }
+
+    // if we "ended" with a d(), we want to sum_muls for the rest of the slice
+    if mul_rest {
+        sum += sum_muls(s);
+    }
+
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        assert_eq!(
+            sum_muls("xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))"),
+            161
+        );
+        assert_eq!(
+            sum_muls_with_do_and_dont(
+                "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))"
+            ),
+            48
+        );
+    }
+}

2024/rust/src/day4.rs

@@ -0,0 +1,126 @@
+mod prelude;
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(4);
+    let grid: Vec<Vec<u8>> = input
+        .trim()
+        .lines()
+        .map(|l| l.trim().bytes().collect())
+        .collect();
+    show_answers(count_xmas(&grid), count_mas_x(&grid));
+}
+
+fn count_xmas(grid: &Vec<Vec<u8>>) -> usize {
+    let height = grid.len();
+    let width = grid[0].len();
+    let mut counter = 0;
+
+    const XMAS: (u8, u8, u8, u8) = (b'X', b'M', b'A', b'S');
+    const SAMX: (u8, u8, u8, u8) = (b'S', b'A', b'M', b'X');
+
+    for (y, line) in grid.iter().enumerate() {
+        for (x, letter) in line.iter().enumerate() {
+            // let near_left_edge = x < 3;
+            let near_top_edge = y < 3;
+            let near_right_edge = x >= width - 3;
+            let near_bottom_edge = y >= height - 3;
+
+            if !near_right_edge && !near_top_edge {
+                // north-west
+                let ray = (
+                    *letter,
+                    grid[y - 1][x + 1],
+                    grid[y - 2][x + 2],
+                    grid[y - 3][x + 3],
+                );
+                if ray == XMAS || ray == SAMX {
+                    counter += 1;
+                }
+            }
+
+            if !near_right_edge {
+                // west
+                let ray = (*letter, grid[y][x + 1], grid[y][x + 2], grid[y][x + 3]);
+                if ray == XMAS || ray == SAMX {
+                    counter += 1;
+                }
+            }
+
+            if !near_right_edge && !near_bottom_edge {
+                // south-west
+                let ray = (
+                    *letter,
+                    grid[y + 1][x + 1],
+                    grid[y + 2][x + 2],
+                    grid[y + 3][x + 3],
+                );
+                if ray == XMAS || ray == SAMX {
+                    counter += 1;
+                }
+            }
+
+            if !near_bottom_edge {
+                // south
+                let ray = (*letter, grid[y + 1][x], grid[y + 2][x], grid[y + 3][x]);
+                if ray == XMAS || ray == SAMX {
+                    counter += 1;
+                }
+            }
+        }
+    }
+    counter
+}
+
+fn count_mas_x(grid: &Vec<Vec<u8>>) -> usize {
+    let mut counter = 0;
+    let (width, height) = (grid[0].len(), grid.len());
+    for y in 1..height - 1 {
+        for x in 1..width - 1 {
+            // 'A' will always be in the middle, so we can easily just look for
+            // middle 'A' occurences and then check for opposing 'S' and 'M'
+            // characters
+            if grid[y][x] != b'A' {
+                continue;
+            }
+
+            // check opposing cross-characters
+            let ray1 = (grid[y - 1][x - 1], grid[y + 1][x + 1]);
+            let ray2 = (grid[y + 1][x - 1], grid[y - 1][x + 1]);
+            if (ray1 == (b'M', b'S') || ray1 == (b'S', b'M'))
+                && (ray2 == (b'M', b'S') || ray2 == (b'S', b'M'))
+            {
+                counter += 1;
+            }
+        }
+    }
+    counter
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = r#"MMMSXXMASM
+MSAMXMSMSA
+AMXSXMAAMM
+MSAMASMSMX
+XMASAMXAMM
+XXAMMXXAMA
+SMSMSASXSS
+SAXAMASAAA
+MAMMMXMMMM
+MXMXAXMASX"#;
+
+        let grid: Vec<Vec<u8>> = input
+            .trim()
+            .lines()
+            .map(|l| l.trim().bytes().collect())
+            .collect();
+
+        assert_eq!(count_xmas(&grid), 18);
+        assert_eq!(count_mas_x(&grid), 9);
+    }
+}

2024/rust/src/day5.rs

@@ -0,0 +1,133 @@
+mod prelude;
+
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(5);
+    let update: ManualUpdate = input.parse().unwrap();
+    show_answers(update.part1(), update.part2());
+}
+
+#[derive(Debug)]
+struct ManualUpdate {
+    rules: HashMap<i64, HashSet<i64>>,
+    updates: Vec<Vec<i64>>,
+}
+
+impl FromStr for ManualUpdate {
+    type Err = ParseIntError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let (rules_string, updates_string) = s.split_once("\n\n").unwrap();
+        let mut rules: HashMap<i64, HashSet<i64>> = HashMap::new();
+        let mut updates = vec![];
+        for rule in rules_string.lines() {
+            let (left, right) = rule.split_once("|").unwrap();
+            let (left, right): (i64, i64) = (left.parse()?, right.parse()?);
+
+            rules.entry(left).or_default().insert(right);
+        }
+        for update in updates_string.lines() {
+            updates.push(
+                update
+                    .split(",")
+                    .map(|page| page.parse())
+                    .collect::<Result<Vec<i64>, Self::Err>>()?,
+            );
+        }
+
+        Ok(Self { rules, updates })
+    }
+}
+
+impl ManualUpdate {
+    fn part1(&self) -> i64 {
+        self.updates
+            .iter()
+            .filter(|update| self.is_update_valid(update))
+            .map(Self::middle_page_number)
+            .sum()
+    }
+
+    fn part2(&self) -> i64 {
+        self.updates
+            .iter()
+            .filter(|update| !self.is_update_valid(update))
+            .map(|update| self.sort_update(update))
+            .map(|sorted_update| Self::middle_page_number(&sorted_update))
+            .sum()
+    }
+
+    fn middle_page_number(update: &Vec<i64>) -> i64 {
+        update[update.len() / 2]
+    }
+
+    fn is_update_valid(&self, update: &Vec<i64>) -> bool {
+        // work through pages in an update backwards
+        for (i, page) in update.iter().rev().enumerate() {
+            // so we can loop through each previous page
+            for previous_page in update[0..update.len() - i].iter().rev() {
+                if let Some(failure_pages) = self.rules.get(page) {
+                    if failure_pages.contains(previous_page) {
+                        return false;
+                    }
+                }
+            }
+        }
+        return true;
+    }
+
+    fn sort_update(&self, update: &Vec<i64>) -> Vec<i64> {
+        let mut sorted_update = update.clone();
+        sorted_update.sort_by(|a, b| {
+            if let Some(after_pages) = self.rules.get(a) {
+                if after_pages.contains(b) {
+                    return Ordering::Less;
+                }
+            }
+            return Ordering::Greater;
+        });
+        sorted_update
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let manual_update: ManualUpdate = "47|53
+97|13
+97|61
+97|47
+75|29
+61|13
+75|53
+29|13
+97|29
+53|29
+61|53
+97|53
+61|29
+47|13
+75|47
+97|75
+47|61
+75|61
+47|29
+75|13
+53|13
+
+75,47,61,53,29
+97,61,53,29,13
+75,29,13
+75,97,47,61,53
+61,13,29
+97,13,75,29,47"
+            .parse()
+            .unwrap();
+        assert_eq!(manual_update.part1(), 143);
+        assert_eq!(manual_update.part2(), 123);
+    }
+}

2024/rust/src/day6.rs

@@ -0,0 +1,193 @@
+mod prelude;
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(6);
+    let mut lab: Lab = input.parse().unwrap();
+    let mut lab2: Lab = input.parse().unwrap();
+    show_answers(
+        lab.num_steps_until_guard_leaves_lab(),
+        lab2.num_positions_of_new_obstructions_that_cause_guard_loop(),
+    );
+}
+
+#[derive(Default, Debug, PartialEq, Eq, Hash, Clone)]
+struct Vec2 {
+    x: i64,
+    y: i64,
+}
+
+impl Vec2 {
+    fn new(x: i64, y: i64) -> Self {
+        Self { x, y }
+    }
+
+    fn add(&self, v: &Vec2) -> Self {
+        Self::new(self.x + v.x, self.y + v.y)
+    }
+}
+
+impl Display for Vec2 {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Vec2({}, {})", self.x, self.y)
+    }
+}
+
+#[derive(Debug, Clone)]
+struct Obstruction {
+    pos: Vec2,
+}
+
+#[derive(Debug, Clone, Hash, PartialEq, Eq)]
+struct Guard {
+    pos: Vec2,
+    vel: Vec2,
+}
+
+impl Guard {
+    fn turn(&mut self) {
+        // too lazy for trig today I guess
+        if self.vel.x > 0 && self.vel.y > 0 {
+            self.vel.x *= -1;
+        } else if self.vel.x < 0 && self.vel.y > 0 {
+            self.vel.y *= -1;
+        } else if self.vel.x < 0 && self.vel.y < 0 {
+            self.vel.x *= -1;
+        } else if self.vel.x > 0 && self.vel.y < 0 {
+            self.vel.y *= -1;
+        } else if self.vel.y != 0 {
+            self.vel.x = self.vel.y * -1;
+            self.vel.y = 0;
+        } else if self.vel.x != 0 {
+            self.vel.y = self.vel.x;
+            self.vel.x = 0;
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+struct Lab {
+    obstructions: Vec<Obstruction>,
+    guard: Guard,
+    size: Vec2,
+}
+
+impl FromStr for Lab {
+    type Err = Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut size = Vec2::default();
+        let mut obstructions = vec![];
+        let mut guard: Option<Guard> = None;
+        for (y, line) in s.lines().enumerate() {
+            size.y += 1;
+            size.x = line.len() as i64; // whatever - still linear ;)
+            for (x, c) in line.bytes().enumerate() {
+                match c {
+                    b'#' => obstructions.push(Obstruction {
+                        pos: Vec2::new(x as i64, y as i64),
+                    }),
+                    b'^' => {
+                        guard = Some(Guard {
+                            pos: Vec2::new(x as i64, y as i64),
+                            vel: Vec2::new(0, -1),
+                        })
+                    }
+                    _ => {}
+                }
+            }
+        }
+        Ok(Lab {
+            size,
+            guard: guard.unwrap(),
+            obstructions,
+        })
+    }
+}
+
+impl Lab {
+    fn step(&mut self) {
+        // move guard
+        let next_pos = self.guard.pos.add(&self.guard.vel);
+        self.guard.pos = next_pos;
+
+        // after moving, check if we need to turn
+        // TODO: obstructions should lookup by position instead of this
+        // broad-phase "check each one each time" slow business
+        while self.has_obstacle_at(&self.guard.pos.add(&self.guard.vel)) {
+            self.guard.turn();
+        }
+    }
+
+    fn contains(&self, pos: &Vec2) -> bool {
+        (0..self.size.x).contains(&pos.x) && (0..self.size.y).contains(&pos.y)
+    }
+
+    fn num_steps_until_guard_leaves_lab(&mut self) -> usize {
+        let mut visited = HashSet::new();
+        visited.insert(self.guard.pos.clone());
+        while self.contains(&self.guard.pos) {
+            self.step();
+            visited.insert(self.guard.pos.clone());
+        }
+        visited.len() - 1
+    }
+
+    fn has_obstacle_at(&self, pos: &Vec2) -> bool {
+        self.obstructions.iter().any(|o| o.pos == *pos)
+    }
+
+    fn num_positions_of_new_obstructions_that_cause_guard_loop(&mut self) -> usize {
+        let mut positions_with_cycles_detected = 0;
+        let mut visited = HashSet::new();
+        visited.insert(self.guard.clone());
+        // TODO: avoid super brute force
+        for x in 0..self.size.x {
+            for y in 0..self.size.y {
+                println!("Simulating at {x} {y}...");
+                let mut alternate_visited = visited.clone();
+                let mut alternate_lab = self.clone();
+                alternate_lab.obstructions.push(Obstruction {
+                    pos: Vec2::new(x, y),
+                });
+                while alternate_lab.contains(&alternate_lab.guard.pos) {
+                    alternate_lab.step();
+                    if alternate_visited.contains(&alternate_lab.guard) {
+                        positions_with_cycles_detected += 1;
+                        break;
+                    }
+                    alternate_visited.insert(alternate_lab.guard.clone());
+                }
+            }
+        }
+        positions_with_cycles_detected
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = "
+....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#..."
+            .trim();
+        let mut lab: Lab = input.parse().unwrap();
+        let mut lab2 = lab.clone();
+        assert_eq!(lab.num_steps_until_guard_leaves_lab(), 41);
+        assert_eq!(
+            lab2.num_positions_of_new_obstructions_that_cause_guard_loop(),
+            6
+        );
+    }
+}

2024/rust/src/day7.rs

@@ -0,0 +1,93 @@
+mod prelude;
+use std::slice::Windows;
+
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(7);
+    show_answers(
+        sum_possibly_valid_tests(&input, &add_and_mul),
+        sum_possibly_valid_tests(&input, &add_and_mul_and_concat),
+    );
+}
+
+fn sum_possibly_valid_tests(input: &str, f: &dyn Fn(Vec<usize>, &usize) -> Vec<usize>) -> usize {
+    let mut sum = 0;
+    for l in input.lines() {
+        let (target, operands) = l.split_once(':').unwrap();
+        let target: usize = target.parse().unwrap();
+        let operands: Vec<usize> = operands
+            .trim()
+            .split(" ")
+            .map(|s| s.parse().unwrap())
+            .collect();
+        if operands
+            .iter()
+            .skip(1)
+            .fold(vec![operands[0]], f)
+            .iter()
+            .any(|n| *n == target)
+        {
+            sum += target;
+        }
+    }
+    sum
+}
+
+fn add_and_mul(lefts: Vec<usize>, right: &usize) -> Vec<usize> {
+    let mut result = vec![];
+    for left in lefts {
+        result.push(left + right);
+        result.push(left * right);
+    }
+    result
+}
+
+fn add_and_mul_and_concat(lefts: Vec<usize>, right: &usize) -> Vec<usize> {
+    let mut result = vec![];
+    for left in lefts {
+        result.push(left + right);
+        result.push(left * right);
+        result.push(format!("{}{}", left, right).parse().unwrap());
+    }
+    result
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        assert_eq!(
+            sum_possibly_valid_tests(
+                "190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20",
+                &add_and_mul
+            ),
+            3749
+        );
+        assert_eq!(
+            sum_possibly_valid_tests(
+                "190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20",
+                &add_and_mul_and_concat
+            ),
+            11387
+        );
+    }
+}

2024/rust/src/day8.rs

@@ -0,0 +1,115 @@
+mod prelude;
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(8);
+    show_answers(part1(&input), part2(&input));
+}
+
+fn part1(input: &str) -> usize {
+    let mut map: HashMap<u8, HashSet<(i64, i64)>> = HashMap::new();
+    let mut antinodes: HashSet<(i64, i64)> = HashSet::new();
+    let (width, height) = (
+        input.lines().count() as i64,
+        input.lines().next().unwrap().len() as i64,
+    );
+    for (y, line) in input.lines().enumerate() {
+        for (x, c) in line.bytes().enumerate() {
+            if c == b'.' {
+                continue;
+            }
+            map.entry(c)
+                .or_insert_with(|| HashSet::new())
+                .insert((x as i64, y as i64));
+        }
+    }
+    for nodes in map.values() {
+        println!("{nodes:?}");
+        for (i, (x1, y1)) in nodes.iter().enumerate() {
+            for (j, (x2, y2)) in nodes.iter().enumerate() {
+                if i == j {
+                    continue;
+                }
+                let (dx, dy) = (x1 - x2, y1 - y2);
+                let (a1x, a1y) = (x1 + dx, y1 + dy);
+                let (a2x, a2y) = (x2 - dx, y2 - dy);
+                if a1x >= 0 && a1x < width && a1y >= 0 && a1y < height {
+                    antinodes.insert((a1x, a1y));
+                }
+                if a2x >= 0 && a2x < width && a2y >= 0 && a2y < height {
+                    antinodes.insert((a2x, a2y));
+                }
+            }
+        }
+    }
+    antinodes.len()
+}
+
+fn part2(input: &str) -> usize {
+    let mut map: HashMap<u8, HashSet<(i64, i64)>> = HashMap::new();
+    let mut antinodes: HashSet<(i64, i64)> = HashSet::new();
+    let (width, height) = (
+        input.trim().lines().count() as i64,
+        input.lines().next().unwrap().trim().len() as i64,
+    );
+    for (y, line) in input.lines().enumerate() {
+        for (x, c) in line.bytes().enumerate() {
+            if c == b'.' {
+                continue;
+            }
+            map.entry(c)
+                .or_insert_with(|| HashSet::new())
+                .insert((x as i64, y as i64));
+        }
+    }
+    for nodes in map.values() {
+        for (i, (x1, y1)) in nodes.iter().enumerate() {
+            for (j, (x2, y2)) in nodes.iter().enumerate() {
+                antinodes.insert((*x1, *y1));
+                antinodes.insert((*x2, *y2));
+                if i == j {
+                    continue;
+                }
+                let (dx, dy) = (x1 - x2, y1 - y2);
+                let (mut a1x, mut a1y) = (x1 + dx, y1 + dy);
+                while a1x >= 0 && a1x < width && a1y >= 0 && a1y < height {
+                    antinodes.insert((a1x, a1y));
+                    println!("{a1x} {a1y} {}", antinodes.len());
+                    a1x += dx;
+                    a1y += dy;
+                }
+                let (mut a2x, mut a2y) = (x2 - dx, y2 - dy);
+                while a2x >= 0 && a2x < width && a2y >= 0 && a2y < height {
+                    antinodes.insert((a2x, a2y));
+                    println!("{a2x} {a2y} {}", antinodes.len());
+                    a2x -= dx;
+                    a2y -= dy;
+                }
+            }
+        }
+    }
+    antinodes.len()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = "............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............";
+        assert_eq!(part1(input), 14);
+        assert_eq!(part2(input), 34);
+    }
+}

2024/rust/src/day9.rs

@@ -0,0 +1,101 @@
+mod prelude;
+pub use crate::prelude::*;
+
+fn main() {
+    let input = day_input(9);
+    show_answers(part1(&input), part2(&input));
+}
+
+struct Disk {
+    blocks: Vec<Option<usize>>,
+    files: Vec<(usize, u8)>,
+    free_blocks: usize,
+}
+
+impl FromStr for Disk {
+    type Err = Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut blocks: Vec<Option<usize>> = vec![];
+        let mut files = vec![];
+        let mut free_blocks: usize = 0;
+        for (i, len) in s.trim().bytes().map(|len| len - b'0').enumerate() {
+            // every other iteration is "free space"
+            let file_id = if i % 2 == 0 {
+                Some((i / 2) as usize)
+            } else {
+                free_blocks += len as usize;
+                None
+            };
+            if file_id.is_some() {
+                files.push((blocks.len(), len));
+            }
+            for _ in 0..len {
+                blocks.push(file_id);
+            }
+        }
+        Ok(Self {
+            files,
+            blocks,
+            free_blocks,
+        })
+    }
+}
+
+impl Disk {
+    fn checksum(&self) -> usize {
+        self.blocks
+            .iter()
+            .enumerate()
+            .map(|(i, b)| i * b.unwrap_or_default())
+            .sum()
+    }
+}
+
+fn part1(input: &str) -> usize {
+    let mut disk: Disk = input.parse().unwrap();
+    let mut right = disk.blocks.len() - 1;
+    for left in 0..(right.clone() - disk.free_blocks + 1) {
+        if disk.blocks[left].is_some() {
+            continue;
+        }
+        while disk.blocks[right].is_none() {
+            right -= 1;
+        }
+        (disk.blocks[left], disk.blocks[right]) = (disk.blocks[right], disk.blocks[left]);
+    }
+
+    disk.checksum()
+}
+
+fn part2(input: &str) -> usize {
+    let mut disk: Disk = input.parse().unwrap();
+    for (cur_i, len) in disk.files.iter().rev() {
+        for left in 0..*cur_i {
+            if disk.blocks[left..(left + (*len as usize))]
+                .iter()
+                .all(|f| f.is_none())
+            {
+                for i in 0..*len {
+                    let i = i as usize;
+                    (disk.blocks[left + i], disk.blocks[cur_i + i]) =
+                        (disk.blocks[cur_i + i], disk.blocks[left + i])
+                }
+                break;
+            }
+        }
+    }
+    disk.checksum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = r#"2333133121414131402"#;
+        assert_eq!(part1(input), 1928);
+        assert_eq!(part2(input), 2858);
+    }
+}

2024/rust/src/prelude.rs

@@ -2,6 +2,9 @@ use std::path::{Path, PathBuf};
 pub use std::{
     cmp::Ordering,
     collections::HashMap,
+    collections::HashSet,
+    convert::Infallible,
+    fmt::Display,
     fs::File,
     io::Read,
     iter::zip,

2024/rust/src/template.rs

@@ -1,22 +1,17 @@
 mod prelude;
-use crate::prelude::*;
+pub use crate::prelude::*;
 
 fn main() {
-    Day5::show(day_input(5), day_input(5))
+    let input = day_input(DAY);
+    show_answers(part1(&input), part2(&input));
 }
 
-struct Day5 {}
-impl AoCSolution for Day5 {
-    type Input = String;
-    type Solution = usize;
-
-    fn part1(input: Self::Input) -> Self::Solution {
+fn part1(input: &str) -> i64 {
     0
-    }
+}
 
-    fn part2(input: Self::Input) -> Self::Solution {
+fn part2(input: &str) -> i64 {
     0
-    }
 }
 
 #[cfg(test)]
@@ -26,7 +21,7 @@ mod tests {
     #[test]
     fn test() {
         let input = r#""#;
-        assert_eq!(Day2::part1(input.into()), 1);
-        assert_eq!(Day2::part2(input.into()), 0);
+        assert_eq!(part1(input), 1);
+        assert_eq!(part2(input), 0);
     }
 }