y2016d1 genuinely don't understand why this was so hard

y2016/resources/1_input.txt

@@ -0,0 +1 @@
+L5, R1, L5, L1, R5, R1, R1, L4, L1, L3, R2, R4, L4, L1, L1, R2, R4, R3, L1, R4, L4, L5, L4, R4, L5, R1, R5, L2, R1, R3, L2, L4, L4, R1, L192, R5, R1, R4, L5, L4, R5, L1, L1, R48, R5, R5, L2, R4, R4, R1, R3, L1, L4, L5, R1, L4, L2, L5, R5, L2, R74, R4, L1, R188, R5, L4, L2, R5, R2, L4, R4, R3, R3, R2, R1, L3, L2, L5, L5, L2, L1, R1, R5, R4, L3, R5, L1, L3, R4, L1, L3, L2, R1, R3, R2, R5, L3, L1, L1, R5, L4, L5, R5, R2, L5, R2, L1, L5, L3, L5, L5, L1, R1, L4, L3, L1, R2, R5, L1, L3, R4, R5, L4, L1, R5, L1, R5, R5, R5, R2, R1, R2, L5, L5, L5, R4, L5, L4, L4, R5, L2, R1, R5, L1, L5, R4, L3, R4, L2, R3, R3, R3, L2, L2, L2, L1, L4, R3, L4, L2, R2, R5, L1, R2

y2016/src/bin/d1.rs

@@ -0,0 +1,20 @@
+use std::fs;
+
+use y2016::days::d1;
+
+fn main() {
+    part1();
+    part2();
+}
+
+fn part1() {
+    let root = env!("CARGO_MANIFEST_DIR");
+    let content = fs::read_to_string(format!("{root}/resources/1_input.txt")).unwrap();
+    println!("{}", d1::process_part1(&content));
+}
+
+fn part2() {
+    let root = env!("CARGO_MANIFEST_DIR");
+    let content = fs::read_to_string(format!("{root}/resources/1_input.txt")).unwrap();
+    println!("{}", d1::process_part2(&content));
+}

y2016/src/days/d1.rs

@@ -0,0 +1,105 @@
+use core::panic;
+use std::collections::{HashMap, HashSet};
+
+#[derive(Clone, Copy, Hash, PartialEq, Eq)]
+enum Orientation {
+    North,
+    East,
+    South,
+    West,
+}
+
+impl Orientation {
+    fn turn(&mut self, direction: &str) {
+        match direction {
+            "R" => match self {
+                Orientation::North => *self = Self::East,
+                Orientation::East => *self = Self::South,
+                Orientation::South => *self = Self::West,
+                Orientation::West => *self = Self::North,
+            },
+            "L" => match self {
+                Orientation::North => *self = Self::West,
+                Orientation::West => *self = Self::South,
+                Orientation::South => *self = Self::East,
+                Orientation::East => *self = Self::North,
+            },
+            _ => panic!("Wrong direction. Only R and L allowed"),
+        }
+    }
+}
+
+pub fn process_part1(input: &str) -> i32 {
+    let mut orientation = Orientation::North;
+    let mut movements = HashMap::new();
+    let mut input = input.to_string();
+    input.pop();
+    for movement in input.split(", ") {
+        let (direction, blocks) = movement.split_at(1);
+        orientation.turn(direction);
+        let blocks = blocks.parse::<i32>().unwrap();
+        movements
+            .entry(orientation)
+            .and_modify(|distance| *distance += blocks)
+            .or_insert(blocks);
+    }
+    let up = movements.get(&Orientation::North).unwrap_or(&0);
+    let down = movements.get(&Orientation::South).unwrap_or(&0);
+    let left = movements.get(&Orientation::West).unwrap_or(&0);
+    let right = movements.get(&Orientation::East).unwrap_or(&0);
+    (up - down).abs() + (left - right).abs()
+}
+
+pub fn process_part2(input: &str) -> i32 {
+    let mut orientation = Orientation::North;
+    let mut visited_coords = HashSet::new();
+    let mut horizontal: i32 = 0;
+    let mut vertical: i32 = 0;
+    let mut input = input.to_string();
+    input.pop();
+    for movement in input.split(", ") {
+        let (direction, blocks) = movement.split_at(1);
+        orientation.turn(direction);
+        let blocks = blocks.parse::<i32>().unwrap();
+        for _block in 1..=blocks {
+            match orientation {
+                Orientation::North => vertical += 1,
+                Orientation::South => vertical -= 1,
+                Orientation::East => horizontal += 1,
+                Orientation::West => horizontal -= 1,
+            }
+            if visited_coords.contains(&(horizontal, vertical)) {
+                return horizontal.abs() + vertical.abs();
+            } else {
+                visited_coords.insert((horizontal, vertical));
+            }
+        }
+    }
+    panic!("Did not find easter bunny hq");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT1: &str = "R2, L3 ";
+    const INPUT2: &str = "R2, R2, R2 ";
+    const INPUT3: &str = "R5, L5, R5, R3 ";
+    const INPUT4: &str = "R8, R4, R4, R8 ";
+
+    #[test]
+    fn part1() {
+        let result = process_part1(INPUT1);
+        assert_eq!(result, 5);
+        let result = process_part1(INPUT2);
+        assert_eq!(result, 2);
+        let result = process_part1(INPUT3);
+        assert_eq!(result, 12);
+    }
+
+    #[test]
+    fn part2() {
+        let result = process_part2(INPUT4);
+        assert_eq!(result, 4);
+    }
+}

y2016/src/days/mod.rs

@@ -0,0 +1 @@
+pub mod d1;

y2016/src/lib.rs

@@ -1 +1 @@
-
+pub mod days;