extended the grid with parsing from string and added position iterator

src/day05.rs

@@ -108,8 +108,8 @@ mod test {
 
     #[test]
     fn test1() {
-        assert!(valid_book(&vec![97, 5, 13], &HashSet::from([(97, 13)])));
-        assert!(!valid_book(&vec![13, 5, 97], &HashSet::from([(97, 13)])));
+        assert!(valid_book(&[97, 5, 13], &HashSet::from([(97, 13)])));
+        assert!(!valid_book(&[13, 5, 97], &HashSet::from([(97, 13)])));
         assert_eq!(part1(TEST_INPUT), 143);
     }
 

src/day06.rs

@@ -1,5 +1,5 @@
 use std::{
-    collections::{HashMap, HashSet},
+    collections::HashSet,
     fs::read_to_string,
 };
 
@@ -60,21 +60,10 @@ fn part2(input: &str) -> RiddleResult {
 }
 
 fn parse(input: &str) -> (Grid<char>, Coord) {
-    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 i64;
-            let y = y as i64;
-            if c == '^' {
-                pos = Some((x, y));
-                m.insert((x, y), '.');
-            } else {
-                m.insert((x, y), c);
-            }
-        });
-    });
-    (Grid::from(m), pos.unwrap())
+    let mut m = Grid::parse(input);
+    let start = m.entries().find(|(_, c)| **c == '^').unwrap().0;
+    m[start] = '.';
+    (m, start)
 }
 
 fn is_loop(m: &Grid<char>, block: Coord, mut pos: Coord, mut dir: char) -> bool {

src/utils/grid.rs

@@ -4,6 +4,7 @@ use std::{
 };
 
 /// A grid structure, indexed by (x, y) tuples. The top-left coordinate is (0, 0).
+#[derive(Eq, PartialEq, Debug)]
 pub struct Grid<T> {
     content_width: i64,
     content_height: i64,
@@ -54,6 +55,34 @@ impl<T> Grid<T> {
     pub fn contains_key(&self, c: Coord) -> bool {
         0 <= c.0 && c.0 < self.content_width && 0 <= c.1 && c.1 < self.content_height
     }
+
+    pub fn entries(&self) -> impl Iterator<Item = (Coord, &T)> {
+        self.content.iter().enumerate().map(|(i, val)| {
+            (
+                (i as i64 % self.content_width, i as i64 / self.content_width),
+                val,
+            )
+        })
+        // .collect_vec()
+    }
+}
+
+impl Grid<char> {
+    pub fn parse(input: &str) -> Grid<char> {
+        let content_width = input.lines().next().unwrap().len();
+        let mut content_height = 0;
+        let mut content = vec![];
+        for line in input.lines() {
+            content_height += 1;
+            content.reserve(content_width);
+            line.chars().for_each(|v| content.push(v));
+        }
+        Grid {
+            content_width: content_width as i64,
+            content_height,
+            content,
+        }
+    }
 }
 
 impl<T> Index<Coord> for Grid<T> {
@@ -73,9 +102,10 @@ impl<T> IndexMut<Coord> for Grid<T> {
 
 #[cfg(test)]
 mod test {
-    use std::collections::HashMap;
+    use itertools::Itertools;
 
     use super::Grid;
+    use std::collections::HashMap;
 
     #[test]
     fn init_and_read() {
@@ -90,6 +120,7 @@ mod test {
         assert_eq!(&'.', grid.get((1, 0)));
         assert_eq!(&'#', grid.get((1, 1)));
     }
+
     #[test]
     fn mutate_by_index() {
         let mut grid = generate();
@@ -106,4 +137,24 @@ mod test {
         ]));
         grid
     }
+
+    #[test]
+    fn from_str() {
+        let s = "..\n.x";
+        let m_str = Grid::parse(s);
+        let mut m_gen = generate();
+        m_gen[(1, 1)] = 'x';
+        assert_eq!(m_gen, m_str);
+    }
+
+    #[test]
+    fn entries() {
+        let v = vec![
+            ((0, 0), &'.'),
+            ((1, 0), &'.'),
+            ((0, 1), &'.'),
+            ((1, 1), &'.'),
+        ];
+        assert_eq!(v, generate().entries().collect_vec());
+    }
 }