Initial commit

70 files changed, 11292 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..1e7caa9
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+Cargo.lock
+target/
diff --git a/d01/Cargo.toml b/d01/Cargo.toml
new file mode 100644
index 0000000..0c0a29c
--- /dev/null
+++ b/d01/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "d01"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/d01/input.txt b/d01/input.txt
new file mode 100644
index 0000000..2c9ac6a
--- /dev/null
+++ b/d01/input.txt
@@ -0,0 +1 @@
+L2, L5, L5, R5, L2, L4, R1, R1, L4, R2, R1, L1, L4, R1, L4, L4, R5, R3, R1, L1, R1, L5, L1, R5, L4, R2, L5, L3, L3, R3, L3, R4, R4, L2, L5, R1, R2, L2, L1, R3, R4, L193, R3, L5, R45, L1, R4, R79, L5, L5, R5, R1, L4, R3, R3, L4, R185, L5, L3, L1, R5, L2, R1, R3, R2, L3, L4, L2, R2, L3, L2, L2, L3, L5, R3, R4, L5, R1, R2, L2, R4, R3, L4, L3, L1, R3, R2, R1, R1, L3, R4, L5, R2, R1, R3, L3, L2, L2, R2, R1, R2, R3, L3, L3, R4, L4, R4, R4, R4, L3, L1, L2, R5, R2, R2, R2, L4, L3, L4, R4, L5, L4, R2, L4, L4, R4, R1, R5, L2, L4, L5, L3, L2, L4, L4, R3, L3, L4, R1, L2, R3, L2, R1, R2, R5, L4, L2, L1, L3, R2, R3, L2, L1, L5, L2, L1, R4
diff --git a/d01/src/main.rs b/d01/src/main.rs
new file mode 100644
index 0000000..3117a5a
--- /dev/null
+++ b/d01/src/main.rs
@@ -0,0 +1,123 @@
+use std::fs;
+
+enum Heading {
+    North,
+    East,
+    South,
+    West,
+}
+
+impl Heading {
+    fn turn_left(&mut self) {
+        *self = match *self {
+            Heading::North => Heading::West,
+            Heading::East  => Heading::North,
+            Heading::South => Heading::East,
+            Heading::West  => Heading::South,
+        };
+    }
+
+    fn turn_right(&mut self) {
+        *self = match *self {
+            Heading::North => Heading::East,
+            Heading::East  => Heading::South,
+            Heading::South => Heading::West,
+            Heading::West  => Heading::North,
+        };
+    }
+}
+
+fn get_route(input: &str) -> Vec<(isize, isize)> {
+    let steps: Vec<&str> = input.trim().split(", ").collect();
+
+    let mut pos = (0, 0);
+    let mut route = vec![pos];
+
+    let mut facing = Heading::North;
+    for s in steps {
+        // Read which way to turn
+        if s.starts_with("L") {
+            facing.turn_left();
+        } else if s.starts_with("R") {
+            facing.turn_right();
+        }
+
+        // Read how far to go in the new direction
+        let dist: usize = s[1..].parse().unwrap();
+
+        // Add each 1-block step to `route' so that part 2 can be solved
+        for _i in 0..dist {
+            pos = match facing {
+                Heading::North => (pos.0 + 1, pos.1),
+                Heading::East  => (pos.0, pos.1 + 1),
+                Heading::South => (pos.0 - 1, pos.1),
+                Heading::West  => (pos.0, pos.1 - 1),
+            };
+            route.push(pos);
+        }
+    }
+
+    route
+}
+
+fn solve_part1(input: &str) -> isize {
+    let route = get_route(input);
+    let ended = route.last().unwrap();
+
+    // Manhattan distance from origin to `ended' position
+    ended.0.abs() + ended.1.abs()
+}
+
+fn solve_part2(input: &str) -> Option<isize> {
+    let route = get_route(input);
+
+    for i in 1..route.len() {
+        let pos = route[i - 1];
+        if route[i..].contains(&pos) {
+            // Manhattan distance to first twice-visited position
+            return Some(pos.0.abs() + pos.1.abs());
+        }
+    }
+
+    None
+}
+
+fn main() {
+    // Read instructions from input text file
+    let input = fs::read_to_string("input.txt").unwrap();
+
+    // Part 1 gives 181 for me
+    println!("Part 1 solution: {}", solve_part1(&input));
+
+    // Part 2 gives 140 for me
+    println!("Part 2 solution: {}", solve_part2(&input).unwrap());
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example1() {
+        let input = "R2, L3";
+        assert_eq!(solve_part1(input), 5);
+    }
+
+    #[test]
+    fn part1_example2() {
+        let input = "R2, R2, R2";
+        assert_eq!(solve_part1(input), 2);
+    }
+
+    #[test]
+    fn part1_example3() {
+        let input = "R5, L5, R5, R3";
+        assert_eq!(solve_part1(input), 12);
+    }
+
+    #[test]
+    fn part2_example1() {
+        let input = "R8, R4, R4, R8";
+        assert_eq!(solve_part2(input).unwrap(), 4);
+    }
+}
diff --git a/d02/Cargo.toml b/d02/Cargo.toml
new file mode 100644
index 0000000..47add02
--- /dev/null
+++ b/d02/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "d02"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/d02/input.txt b/d02/input.txt
new file mode 100644
index 0000000..ba5a73d
--- /dev/null
+++ b/d02/input.txt
@@ -0,0 +1,5 @@
+RUDULRLLUULRURDDRRUDURULLLDRLRLUDDLUDUDDUDRRDUDULDUUULLRULLRLDDLDLDDRLRRRRUDLLDDUULDRLLUDDRRUURLULRRRDLLURRUUDURUDDURLUDDDLUDDUUDUURUDLRDRDRLRDRLDRUDRUUDLRDDRRURDDLRDDRRURDUDDLULLUDRURURRRLRRUDUULULULRRLDLUDUURRLLRUDLLDRDDLRRRULRUDLULDDLLLULDLRUDLLLLRDDLRDRLDRLLRDRRDLRDULULRLLLDRUDRRRUULRUULDRURLUDRURRDLLDLRDLDDDDRRLUDLRRLUUUURDRDDLRRURURRDUULLRLURLURUDDDRDURDUUDRLRLRRLDDLDLDLDDDUDDULURLDDLLRLRRDULUDDLULRLUDDLDLRULUUUDRLDRUDURLUDDRLLRUULDLRRRRDLLLLURULLRDRRUDLUULRRDLLRLRLUDLDDULLDLLRDLDLL
+LLUUUUUUDUDRLRDRDLDURRRLLRRLRURLLUURRLLUDUDLULUURUUURDLUDLDDLULLRDLRUULDLRDUDURLLDDUDUDULLUDDUULLLUULRRRLULRURRDLRUDUDDURRRDRUURDURLLULLRULLDRUULLURLDRDUUDDDDDDRRLDRLRRRLULDDUURRLLLLDRURLURDRDRDURUDUURRDUDUDRLLUUDDRLUDDDRDLDLRLDRURRDLLRULDRLLURURRLUULLRLRRURDDRDRUUURUURUUUDLLRRLUDRLDLRLURLDLUDDUDDDLDUDRRLDLRURULRLLRDUULURRRULDLLLRLDDDUURRRRDULLRURRLULULDLRRUDUDDLRUURDLDUDDUDRRDLRRRDUDUUUDLLDDDDLURLURRRUUULLLULRRLLLLLLULDUUDLRUDRRDLRDUUDUDLLRLDLLRUURDUUURUUUDDLLUUDLULDURLULULUUUDRUDULLURRULRULLRDLDDU
+RLUUURULLDLRLDUDRDURRDUURLLUDDDUULRRRLRLURDDRUULUDULDUUDDDDUDDDDRUDDLDUUDRUDLRRRLLRDDLLLRLLRUULRUULDDRURRLURRLRLULDDRRRDDURDDRDRDULRUDRUUDULRLLULDLRLLDRULRDDRRDDUDLRLLUDRDRRRLUDULRDLRDDURRUUDDRRUDURRUUUDDRRDUDURLUUDUDUURDDDLURLULLUULULURUDUUDRUDULLUUULURDLDUULLDDLLDULRLRLRDUUURUUDLRLDURUDRLDULLUDLDLLRDUURRDUDURLUUUDLLRRULRLULRLDLLURDURRULRLLRRDUDLLRDRRRRDLUUDRUUUDDLRLUDDDDDDRURRRUUURRDLLRURLDDLLDLRRLLLDRRULRRUDLDRDDRRLULURLLUURURURRRRUUUUURUDURLRLLLULULDLLDLRDRRULUDUDRDRRDRDRRDUDLLLRUDRUDDDULRULRRRDRLRUUUURUDURDUUULLULRUDDULDUUDLDURRD
+ULRULDDLDLULLLRRRLRUDDDDDLLDDUDLRRDULUUDRDLRRURDRRLUULRURUDRRULDLLLUDRUUDULULUDDRUDDDRDURRRDRDUUURLRDULUDRDRLDRUDDLLLDRRULUDLUDLDLLRRUDUULULDLDLLUURDLDDLLUUDURLURLLLDRDLDRRLRULUURRDRULRUUURULRRUDDDDLLDLDDLLRRLRRRRDUUDUDLDRDRRURDLRURULDLRDLLLLRUDRLLRDLRLRDURDRUDURRRLRDRDLLRLUDDDDRLRLLDUURRURLUURUULUDLUURDRRUDDLUDUDDDURRDRUDRLRULDULUUUUUUDDUDRUDUUURUDRRDLUDLUUDUULUDURDLDDDLLURRURUUDUDDRRDRLLULULDRLRURRDDDRDUUURDDDRULUDRDDLDURRLDDDLRRRLDDRDURULDLUDLLLURLURRLRRULDLLDDUDRRULDRRRRLURRUULRRRUDLURDLLDLLDULUUDRRLDLLLDRLRUDLUULDLDRUDUDURDRUDRDDDLRLULLUR
+LRLUUURRLRRRRRUURRLLULRLULLDLUDLUDRDDRLDLRLULLURDURLURDLLRLDUUDDURRRRLDLLRULLRLDLLUUDRLDDLLDRULDRLLRURDLRURRUDLULLRURDLURRURUDULLDRLLUUULUDRURRUUDUDULUUULRLDDULDRDLUDDUDDDLRURULLDLLLRLLUURDLRUDLLLLDLLRLRUUUDDRUUUUDLDLRDDURLDURUULLLUUDLLLLDULRRRLLDLDRRDRLUDRUDURLLUDLRLLUDUDRDDDRDLRDLRULUULDRLUDLRLDUURLRRLUDDDUUDDDUDRLDLDUDLURUULLDDDURUUULRLUDLDURUUDRDRURUDDUURDUUUDLLDLDLDURUURLLLLRURUURURULRULLRUDLRRUUUUUDRRLLRDDUURDRDRDDDUDRLURDRRRUDLLLDURDLUUDLLUDDULUUDLDUUULLDRDLRURUURRDURRDLURRRRLLUUULRDULDDLDUURRDLDLLULRRLLUDLDUDLUUL
diff --git a/d02/src/main.rs b/d02/src/main.rs
new file mode 100644
index 0000000..33c7ec0
--- /dev/null
+++ b/d02/src/main.rs
@@ -0,0 +1,86 @@
+use std::fs;
+
+fn solve_part1(lines: &Vec<&str>) -> String {
+    let mut result = String::new();
+
+    let mut num = 5;
+    for line in lines {
+        for c in line.chars() {
+            num = match c {
+                'U' => if num - 3 >  0 { num - 3 } else { num },
+                'D' => if num + 3 < 10 { num + 3 } else { num },
+                'L' => if num % 3 != 1 { num - 1 } else { num },
+                'R' => if num % 3 != 0 { num + 1 } else { num },
+                _   => num, // shouldn't happen
+            }
+        }
+        result.push_str(&num.to_string());
+    }
+
+    result
+}
+
+fn solve_part2(lines: &Vec<&str>) -> String {
+    let mut result = String::new();
+
+    // Part 2's keypad is a bit more exotic
+    let keypad = [
+        [0,  0,  1,  0,  0],
+        [0,  2,  3,  4,  0],
+        [5,  6,  7,  8,  9],
+        [0, 10, 11, 12,  0],
+        [0,  0, 13,  0,  0],
+    ];
+    let mut pos = (2, 0); // (row, col) index
+
+    for line in lines {
+        for c in line.chars() {
+            let mut new = pos;
+            match c {
+                'U' => new.0 = if pos.0 > 0 { pos.0 - 1 } else { pos.0 },
+                'D' => new.0 = if pos.0 < 4 { pos.0 + 1 } else { pos.0 },
+                'L' => new.1 = if pos.1 > 0 { pos.1 - 1 } else { pos.1 },
+                'R' => new.1 = if pos.1 < 4 { pos.1 + 1 } else { pos.1 },
+                _   => {}, // shouldn't happen
+            };
+            // Ignore this `c' if it would take us off the diamond's edge
+            if keypad[new.0][new.1] != 0 {
+                pos = new;
+            }
+        }
+
+        // Print as hexadecimal to follow puzzle description
+        result.push_str(&format!("{:X}", keypad[pos.0][pos.1]));
+    }
+
+    result
+}
+
+fn main() {
+    // Read directions from input text file
+    let input = fs::read_to_string("input.txt").unwrap();
+    let lines = input.lines().collect();
+
+    // Part 1 gives 74921 for me
+    println!("Part 1 solution: {}", solve_part1(&lines));
+
+    // Part 2 gives A6B35 for me
+    println!("Part 2 solution: {}", solve_part2(&lines));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example1() {
+        let lines = vec!["ULL", "RRDDD", "LURDL", "UUUUD"];
+        assert_eq!(solve_part1(&lines), "1985");
+    }
+
+    #[test]
+    fn part2_example1() {
+        let lines = vec!["ULL", "RRDDD", "LURDL", "UUUUD"];
+        assert_eq!(solve_part2(&lines), "5DB3");
+    }
+}
diff --git a/d03/Cargo.toml b/d03/Cargo.toml
new file mode 100644
index 0000000..5bff35d
--- /dev/null
+++ b/d03/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "d03"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/d03/input.txt b/d03/input.txt
new file mode 100644
index 0000000..b8e5272
--- /dev/null
+++ b/d03/input.txt
@@ -0,0 +1,1911 @@
+  541  588  421
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