day 6 part 1

src/day06.rs

@@ -1,4 +1,7 @@
-use std::fs::read_to_string;
+use std::{
+    collections::{HashMap, HashSet},
+    fs::read_to_string,
+};
 
 pub fn day_main() {
     let input = read_to_string("input/day06.txt").unwrap();
@@ -7,10 +10,54 @@ pub fn day_main() {
     println!(" part2: {}", part2(input));
 }
 
-type RiddleResult = i64;
+type RiddleResult = usize;
 
 fn part1(input: &str) -> RiddleResult {
-    0
+    let mut m = HashMap::new();
+    let mut pos = None;
+    input.lines().enumerate().for_each(|(y, line)| {
+        line.char_indices().for_each(|(x, c)| {
+            let x = x as i32;
+            let y = y as i32;
+            if c == '^' {
+                pos = Some((x, y));
+                m.insert((x, y), '.');
+            } else {
+                m.insert((x, y), c);
+            }
+        });
+    });
+
+    let mut result = 0;
+    let mut pos = pos.unwrap();
+    let mut dir = '^';
+    let mut visited = HashSet::new();
+    while m.contains_key(&pos) {
+        let (x, y) = pos;
+        // println!("at {x},{y} {dir}");
+        visited.insert(pos);
+        result += 1;
+        let next = match dir {
+            '^' => (x, y - 1),
+            'v' => (x, y + 1),
+            '<' => (x - 1, y),
+            '>' => (x + 1, y),
+            _ => unreachable!(),
+        };
+        if let Some('#') = m.get(&next) {
+            // println!("bump at {x},{y}");
+            dir = match dir {
+                '^' => '>',
+                'v' => '<',
+                '<' => '^',
+                '>' => 'v',
+                _ => unreachable!("asdf"),
+            };
+        } else {
+            pos = next;
+        }
+    }
+    visited.len()
 }
 
 fn part2(_input: &str) -> RiddleResult {
@@ -21,11 +68,21 @@ fn part2(_input: &str) -> RiddleResult {
 mod test {
     use super::{part1, part2};
 
-    const TEST_INPUT: &str = r"";
+    const TEST_INPUT: &str = r"....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#...
+";
 
     #[test]
     fn test1() {
-        assert_eq!(part1(TEST_INPUT), 0);
+        assert_eq!(part1(TEST_INPUT), 41);
     }
 
     #[test]