Lots of progress on day 8 part 1

day8/README.md

@@ -4,7 +4,7 @@
 
 The expedition comes across a peculiar patch of tall trees all planted carefully in a grid. The Elves explain that a previous expedition planted these trees as a reforestation effort. Now, they're curious if this would be a good location for a tree house.
 
-First, determine whether there is enough tree cover here to keep a tree house hidden. To do this, you need to count the number of trees that are visible from outside the grid when looking directly along a row or column.
+First, determine whether there is enough tree cover here to keep a tree house **hidden**. To do this, you need to count the number of trees that are **visible from outside the grid** when looking directly along a row or column.
 
 The Elves have already launched a quadcopter to generate a map with the height of each tree (your puzzle input). For example:
 
@@ -16,18 +16,18 @@ The Elves have already launched a quadcopter to generate a map with the height o
 
 Each tree is represented as a single digit whose value is its height, where 0 is the shortest and 9 is the tallest.
 
-A tree is visible if all of the other trees between it and an edge of the grid are shorter than it. Only consider trees in the same row or column; that is, only look up, down, left, or right from any given tree.
+A tree is **visible** if all of the other trees between it and an edge of the grid are **shorter** than it. Only consider trees in the same row or column; that is, only look up, down, left, or right from any given tree.
 
-All of the trees around the edge of the grid are visible - since they are already on the edge, there are no trees to block the view. In this example, that only leaves the interior nine trees to consider:
+All of the trees around the edge of the grid are **visible** - since they are already on the edge, there are no trees to block the view. In this example, that only leaves the **interior nine trees** to consider:
 
-* The top-left 5 is visible from the left and top. (It isn't visible from the right or bottom since other trees of height 5 are in the way.)
-* The top-middle 5 is visible from the top and right.
-* The top-right 1 is not visible from any direction; for it to be visible, there would need to only be trees of height 0 between it and an edge.
-* The left-middle 5 is visible, but only from the right.
+* The top-left 5 is **visible** from the left and top. (It isn't visible from the right or bottom since other trees of height 5 are in the way.)
+* The top-middle 5 is **visible** from the top and right.
+* The top-right 1 is not visible from any direction; for it to be visible, there would need to only be trees of height **0** between it and an edge.
+* The left-middle 5 is **visible**, but only from the right.
 * The center 3 is not visible from any direction; for it to be visible, there would need to be only trees of at most height 2 between it and an edge.
-* The right-middle 3 is visible from the right.
-* In the bottom row, the middle 5 is visible, but the 3 and 4 are not.
+* The right-middle 3 is **visible** from the right.
+* In the bottom row, the middle 5 is **visible**, but the 3 and 4 are not.
 
 With 16 trees visible on the edge and another 5 visible in the interior, a total of 21 trees are visible in this arrangement.
 
-Consider your map; how many trees are visible from outside the grid?
+**Consider your map; how many trees are visible from outside the grid?**

day8/src/main.rs

@@ -1,8 +1,203 @@
+use std::collections::HashSet;
+
+#[derive(Debug, Copy, Clone, PartialOrd, PartialEq, Eq, Hash)]
+enum VisibleDirection {
+    Top,
+    Bottom,
+    Left,
+    Right,
+}
+
+use VisibleDirection::*;
+
+#[derive(Debug, Default)]
+struct Tree {
+    height: usize,
+    visible: HashSet<VisibleDirection>,
+}
+
+impl Tree {
+    fn new(height: usize) -> Self {
+        Tree {
+            height,
+            ..Tree::default()
+        }
+    }
+
+    fn is_visible(&self) -> bool {
+        !self.visible.is_empty()
+    }
+
+    fn set_visible(&mut self, dir: VisibleDirection) -> &mut Self {
+        self.visible.insert(dir);
+
+        self
+    }
+
+    fn set_all_visible(&mut self) -> &mut Self {
+        self.set_visible(Top)
+            .set_visible(Bottom)
+            .set_visible(Left)
+            .set_visible(Right)
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+#[derive(Debug)]
+struct Grid<T> {
+    width: usize,
+    vec: Vec<T>,
+}
+
+impl<T> Grid<T> {
+    fn new(width: usize) -> Self {
+        Grid {
+            width,
+            vec: Vec::new(),
+        }
+    }
+
+    // Convert x,y coordinate into linear array index
+    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) {
+        (idx % self.width, idx / self.width)
+    }
+
+    fn row_first_idx(&self, row: usize) -> usize {
+        let idx = row * self.width;
+
+        if idx < self.vec.len() {
+            idx
+        } else {
+            self.vec.len()
+        }
+    }
+
+    fn row_last_idx(&self, row: usize) -> usize {
+        if (row + 1) > self.num_rows() {
+            return self.vec.len();
+        }
+
+        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
+        }
+    }
+
+    fn num_cols(&self) -> usize {
+        self.width
+    }
+
+    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> {
+        let mut indexes = Vec::new();
+
+        if col_num > self.num_cols() {
+            return indexes;
+        }
+
+        for r in 0..self.num_rows() {
+            let idx = self.width * r + col_num;
+            indexes.push(idx);
+        }
+
+        indexes
+    }
+}
+
+impl Grid<Tree> {
+    fn mark_outer_trees_visible(&mut self) {
+        fn set_row_visible(row: &mut [Tree]) {
+            row.iter_mut().for_each(|tree| { tree.set_all_visible(); })
+        }
+
+        // Set top/bottom rows as visible
+        set_row_visible(self.get_row(0));
+        set_row_visible(self.get_row(self.num_rows() - 1));
+
+        // Set left/right cols as visible
+        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();
+        });
+    }
+
+    fn mark_visible_trees(&mut self) {
+        self.mark_outer_trees_visible();
+    }
+
+    pub fn get_visible_trees(&self) -> usize {
+        self
+            .vec
+            .iter()
+            .filter(|tree| tree.is_visible())
+            .collect::<Vec<&Tree>>()
+            .len()
+    }
+
+    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);
+
+        for line in lines {
+            let mut row: Vec<Tree> = line
+                .chars()
+                .map(|ch| Tree::new(ch.to_digit(10).unwrap() as usize))
+                .collect();
+
+            grid.vec.append(&mut row);
+        }
+
+        grid
+    }
+}
+
+// ----------------------------------------------------------------------------
+
 fn main() {
     let file_str = include_str!("input.txt");
+    let mut grid = Grid::from_file_str(file_str);
+    grid.mark_visible_trees();
+    let visible_num = grid.get_visible_trees();
+
+    println!("Part 1: Number of visible trees: {}", visible_num);
+
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
-}
+
+    fn get_data() -> &'static str {
+        include_str!("test-input.txt")
+    }
+
+    #[test]
+    fn test_outer_visible_trees() {
+        let mut grid = Grid::from_file_str(get_data());
+        grid.mark_outer_trees_visible();
+
+        assert_eq!(grid.get_visible_trees(), 16usize);
+    }
+}

day8/src/test-input.txt

@@ -0,0 +1,5 @@
+30373
+25512
+65332
+33549
+35390