Complete day 8 part 1

day8/src/main.rs

@@ -51,7 +51,7 @@ struct Grid<T> {
 }
 
 impl<T> Grid<T> {
-    fn new(width: usize) -> Self {
+    pub fn new(width: usize) -> Self {
         Grid {
             width,
             vec: Vec::new(),
@@ -59,16 +59,16 @@ impl<T> Grid<T> {
     }
 
     // Convert x,y coordinate into linear array index
-    fn xy_idx(&self, x: usize, y: usize) -> usize {
+    pub fn xy_idx(&self, x: usize, y: usize) -> usize {
         (y * self.width) + x
     }
 
     /// Convert linear array index to x,y coordinate
-    fn idx_xy(&self, idx: usize) -> (usize, usize) {
+    pub fn idx_xy(&self, idx: usize) -> (usize, usize) {
         (idx % self.width, idx / self.width)
     }
 
-    fn row_first_idx(&self, row: usize) -> usize {
+    pub fn row_first_idx(&self, row: usize) -> usize {
         let idx = row * self.width;
 
         if idx < self.vec.len() {
@@ -78,7 +78,7 @@ impl<T> Grid<T> {
         }
     }
 
-    fn row_last_idx(&self, row: usize) -> usize {
+    pub fn row_last_idx(&self, row: usize) -> usize {
         if (row + 1) > self.num_rows() {
             return self.vec.len();
         }
@@ -86,32 +86,37 @@ impl<T> Grid<T> {
         self.row_first_idx(row + 1) - 1
     }
 
-    fn num_rows(&self) -> usize {
-        let even_rows = self.vec.len() / self.width;
-
-        if self.vec.len() % self.width > 0 {
-            even_rows + 1
-        } else {
-            even_rows
-        }
+    pub fn num_rows(&self) -> usize {
+        self.vec.len() / self.width
     }
 
-    fn num_cols(&self) -> usize {
+    pub fn num_cols(&self) -> usize {
         self.width
     }
 
-    fn get_row(&mut self, row_num: usize) -> &mut [T] {
+    pub fn get_row(&mut self, row_num: usize) -> &mut [T] {
         let start = self.row_first_idx(row_num);
         let end = self.row_last_idx(row_num);
 
         &mut self.vec[start..=end]
     }
 
-    fn get_column_indexes(&self, col_num: usize) -> Vec<usize> {
+    pub fn get_row_indexes(&self, row_num: usize) -> Vec<usize> {
+        let start = self.row_first_idx(row_num);
+        let end = self.row_last_idx(row_num);
+
+        (start..=end).collect()
+    }
+
+    pub fn get_column_indexes(&self, col_num: usize) -> Vec<usize> {
         let mut indexes = Vec::new();
 
-        if col_num > self.num_cols() {
-            return indexes;
+        if col_num >= self.num_cols() {
+            panic!(
+                "Asked for column {}, there are {} columns",
+                col_num,
+                self.num_cols()
+            );
         }
 
         for r in 0..self.num_rows() {
@@ -124,9 +129,11 @@ impl<T> Grid<T> {
 }
 
 impl Grid<Tree> {
-    fn mark_outer_trees_visible(&mut self) {
+    fn mark_outer_trees_visible(&mut self) -> &mut Self {
         fn set_row_visible(row: &mut [Tree]) {
-            row.iter_mut().for_each(|tree| { tree.set_all_visible(); })
+            row.iter_mut().for_each(|tree| {
+                tree.set_all_visible();
+            })
         }
 
         // Set top/bottom rows as visible
@@ -137,25 +144,79 @@ impl Grid<Tree> {
         self.get_column_indexes(0).into_iter().for_each(|id| {
             self.vec[id].set_all_visible();
         });
-        self.get_column_indexes(self.num_cols() - 1).into_iter().for_each(|id| {
-            self.vec[id].set_all_visible();
-        });
+        self.get_column_indexes(self.num_cols() - 1)
+            .into_iter()
+            .for_each(|id| {
+                self.vec[id].set_all_visible();
+            });
+
+        self
     }
 
-    fn mark_visible_trees(&mut self) {
-        self.mark_outer_trees_visible();
+    fn mark_visible(&mut self, dir: VisibleDirection) -> &mut Self {
+        let indexes: Vec<Vec<usize>> = match dir {
+            Top | Bottom => {
+                // Skip outer columns, as those are already marked visible
+                (1..(self.num_cols() - 1))
+                    .map(|c| self.get_column_indexes(c))
+                    .map(|column| {
+                        if dir == Bottom {
+                            column.into_iter().rev().collect()
+                        } else {
+                            column
+                        }
+                    })
+                    .collect()
+            }
+            Left | Right => {
+                // Skip first and last rows, as those are already marked visible
+                (1..(self.num_rows() - 1))
+                    .map(|r| self.get_row_indexes(r))
+                    .map(|row| {
+                        if dir == Right {
+                            row.into_iter().rev().collect()
+                        } else {
+                            row
+                        }
+                    })
+                    .collect()
+            }
+        };
+
+        for row_or_col in indexes {
+            let mut tallest = 0usize;
+
+            for idx in row_or_col {
+                let tree = &mut self.vec[idx];
+
+                if tallest < tree.height {
+                    tree.set_visible(dir);
+
+                    tallest = tree.height;
+                }
+            }
+        }
+
+        self
+    }
+
+    pub fn mark_visible_trees(&mut self) {
+        self.mark_outer_trees_visible()
+            .mark_visible(Top)
+            .mark_visible(Right)
+            .mark_visible(Bottom)
+            .mark_visible(Left);
     }
 
     pub fn get_visible_trees(&self) -> usize {
-        self
-            .vec
+        self.vec
             .iter()
             .filter(|tree| tree.is_visible())
             .collect::<Vec<&Tree>>()
             .len()
     }
 
-    fn from_file_str(file_str: &'static str) -> Grid<Tree> {
+    pub fn from_file_str(file_str: &'static str) -> Grid<Tree> {
         let lines: Vec<&str> = file_str.lines().collect();
         let width = lines[0].len();
         let mut grid: Grid<Tree> = Grid::new(width);
@@ -182,7 +243,6 @@ fn main() {
     let visible_num = grid.get_visible_trees();
 
     println!("Part 1: Number of visible trees: {}", visible_num);
-
 }
 
 #[cfg(test)]
@@ -193,6 +253,34 @@ mod tests {
         include_str!("test-input.txt")
     }
 
+    #[test]
+    fn test_row_first_index() {
+        let grid = Grid::from_file_str(get_data());
+
+        assert_eq!(grid.row_first_idx(1), 5);
+        assert_eq!(grid.row_first_idx(0), 0);
+        assert_eq!(grid.row_first_idx(2), 10);
+    }
+
+    #[test]
+    fn test_row_last_index() {
+        let grid = Grid::from_file_str(get_data());
+
+        assert_eq!(grid.row_last_idx(0), 4);
+        assert_eq!(grid.row_last_idx(1), 9);
+    }
+
+    #[test]
+    fn test_get_column_indexes() {
+        let mut grid = Grid::from_file_str(get_data());
+
+        assert_eq!(grid.width, 5);
+
+        assert_eq!(grid.get_column_indexes(0), vec![0, 5, 10, 15, 20]);
+        assert_eq!(grid.get_column_indexes(1), vec![1, 6, 11, 16, 21]);
+        assert_eq!(grid.get_column_indexes(4), vec![4, 9, 14, 19, 24]);
+    }
+
     #[test]
     fn test_outer_visible_trees() {
         let mut grid = Grid::from_file_str(get_data());
@@ -200,4 +288,27 @@ mod tests {
 
         assert_eq!(grid.get_visible_trees(), 16usize);
     }
+
+    #[test]
+    fn test_visible_trees() {
+        let mut grid = Grid::from_file_str(get_data());
+        grid.mark_visible_trees();
+
+        let visible = [(1usize, 1usize), (2, 1), (1, 2), (4, 3), (2, 3)];
+
+        for (x, y) in visible {
+            let idx = grid.xy_idx(x, y);
+
+            assert!(
+                grid.vec[idx].is_visible(),
+                "Tree {}({},{}) should be visible: {:#?}",
+                idx,
+                x,
+                y,
+                grid.vec[idx]
+            );
+        }
+
+        assert_eq!(grid.get_visible_trees(), 21usize);
+    }
 }