Added 2022, first few problems

3 files changed, 102 insertions, 0 deletions

diff --git a/2022/08/a.rs b/2022/08/a.rs
new file mode 100644
index 0000000..b145486
--- /dev/null
+++ b/2022/08/a.rs
@@ -0,0 +1,42 @@
+use std::cmp::max;
+mod common;
+use common::*;
+
+fn mark_visible(grid: &mut Grid) {
+    let update = |elem: &mut (i8, bool), m: &mut i8| {
+        elem.1 = elem.1 || elem.0 > *m;
+        *m = max(*m, elem.0);
+    };
+
+    for row in &mut *grid {
+        // From left
+        let mut m = -1;
+        for t in &mut *row { update(t, &mut m); }
+
+        // From right
+        let mut m = -1;
+        for t in &mut row.iter_mut().rev() { update(t, &mut m); }
+    }
+
+    for j in 0..grid[0].len() {
+        // From top
+        let mut m = -1;
+        for i in 0..grid.len() { update(&mut grid[i][j], &mut m); }
+
+        // From bottom
+        let mut m = -1;
+        for i in (0..grid.len()).rev() { update(&mut grid[i][j], &mut m); }
+    }
+}
+
+fn count_visible(grid: &Grid) -> usize {
+    grid.iter()
+        .map(|row| row.iter().filter(|c| c.1).count())
+        .sum()
+}
+
+fn main() {
+    let mut grid = read_grid_from_stdin();
+    mark_visible(&mut grid);
+    println!("{}", count_visible(&grid));
+}
diff --git a/2022/08/b.rs b/2022/08/b.rs
new file mode 100644
index 0000000..5f7bce8
--- /dev/null
+++ b/2022/08/b.rs
@@ -0,0 +1,47 @@
+use std::cmp::max;
+mod common;
+use common::*;
+
+fn count_visible_from(grid: &Grid, i0: usize, j0: usize) -> usize {
+    let x = grid[i0][j0].0;
+    let mut top = 0;
+    for i in (0..i0).rev() {
+        top += 1;
+        if grid[i][j0].0 >= x { break; }
+    }
+
+    let mut bottom = 0;
+    for i in i0+1..grid.len() {
+        bottom += 1;
+        if grid[i][j0].0 >= x { break; }
+    }
+
+    let mut left = 0;
+    for j in (0..j0).rev() {
+        left += 1;
+        if grid[i0][j].0 >= x { break; }
+    }
+
+    let mut right = 0;
+    for j in j0+1..grid[0].len() {
+        right += 1;
+        if grid[i0][j].0 >= x { break; }
+    }
+
+    top * bottom * left * right
+}
+
+fn max_view_factor(grid: &Grid) -> usize {
+    let mut m = 0;
+    for i in 0..grid.len() {
+        for j in 0..grid[0].len() {
+            m = max(m, count_visible_from(grid, i, j));
+        }
+    }
+    m
+}
+
+fn main() {
+    let grid = read_grid_from_stdin();
+    println!("{}", max_view_factor(&grid));
+}
diff --git a/2022/08/common.rs b/2022/08/common.rs
new file mode 100644
index 0000000..45fbf10
--- /dev/null
+++ b/2022/08/common.rs
@@ -0,0 +1,13 @@
+pub type Grid = Vec<Vec<(i8, bool)>>;
+
+pub fn read_grid_from_stdin() -> Grid {
+    let mut grid = Vec::<Vec<(i8, bool)>>::new();
+    let mut line = String::new();
+    while std::io::stdin().read_line(&mut line).unwrap() > 0 {
+        let row = line[..line.len()-1].as_bytes().iter()
+            .map(|b| ((*b as i8) - ('0' as i8), false)).collect();
+        grid.push(row);
+        line.clear();
+    }
+    grid
+}