day(14): add solution

Signed-off-by: Matej Focko <mfocko@redhat.com>

samples/day14.txt

@@ -0,0 +1,10 @@
+O....#....
+O.OO#....#
+.....##...
+OO.#O....O
+.O.....O#.
+O.#..O.#.#
+..O..#O..O
+.......O..
+#....###..
+#OO..#....

src/bin/day14.rs

@@ -0,0 +1,142 @@
+use std::collections::HashMap;
+
+use aoc_2023::*;
+use indicatif::ProgressIterator;
+use memoize::memoize;
+
+type Output1 = usize;
+type Output2 = Output1;
+
+#[memoize]
+fn slide_rocks(map: Vec<Vec<char>>) -> Vec<Vec<char>> {
+    let mut tilted: Vec<Vec<char>> = map.to_vec();
+
+    for x in 0..tilted[0].len() {
+        let mut next = 0;
+        for y in 0..tilted.len() {
+            match tilted[y][x] {
+                '#' | 'O' => {
+                    next = y + 1;
+                }
+                '.' => {
+                    while next < tilted.len() && tilted[next][x] == '.' {
+                        next += 1;
+                    }
+
+                    if next < tilted.len() && tilted[next][x] == 'O' {
+                        tilted[y][x] = 'O';
+                        tilted[next][x] = '.';
+                    }
+                }
+                _ => unreachable!(),
+            }
+        }
+    }
+
+    tilted
+}
+
+#[memoize]
+fn rotate_east(map: Vec<Vec<char>>) -> Vec<Vec<char>> {
+    let mut r = map.clone();
+
+    for y in 0..map.len() {
+        for (x, row) in r.iter_mut().enumerate().take(map[y].len()) {
+            row[map.len() - y - 1] = map[y][x];
+        }
+    }
+
+    r
+}
+
+#[memoize]
+fn run_cycle(map: Vec<Vec<char>>) -> Vec<Vec<char>> {
+    let mut map = map;
+    for _ in 0..4 {
+        map = slide_rocks(map);
+        map = rotate_east(map);
+    }
+
+    map
+}
+
+fn total_load(m: &[Vec<char>]) -> usize {
+    let rows = m.len();
+
+    m.iter()
+        .enumerate()
+        .map(|(y, l)| (rows - y) * l.iter().filter(|&&c| c == 'O').count())
+        .sum()
+}
+
+struct Day14 {
+    map: Vec<Vec<char>>,
+}
+
+impl Solution<Output1, Output2> for Day14 {
+    fn new<P: AsRef<Path>>(pathname: P) -> Self {
+        let lines: Vec<String> = file_to_lines(pathname);
+
+        Self {
+            map: lines.iter().map(|l| l.chars().collect()).collect(),
+        }
+    }
+
+    fn part_1(&mut self) -> Output1 {
+        let tilted = slide_rocks(self.map.clone());
+        total_load(&tilted)
+    }
+
+    fn part_2(&mut self) -> Output2 {
+        let mut map = self.map.clone();
+
+        let iterations = 1000000000;
+        let mut remaining = 0;
+
+        let mut seen: HashMap<Vec<Vec<char>>, usize> = HashMap::new();
+        for i in (0..iterations).progress() {
+            seen.insert(map.clone(), i);
+            map = run_cycle(map);
+
+            if let Some(&old_i) = seen.get(&map) {
+                remaining = (iterations - i - 1) % (i - old_i + 1);
+                break;
+            }
+        }
+
+        for _ in 0..remaining {
+            map = run_cycle(map);
+        }
+
+        total_load(&map)
+    }
+}
+
+fn main() -> Result<()> {
+    Day14::main()
+}
+
+test_sample!(day_14, Day14, 136, 64);
+
+#[cfg(test)]
+mod day_14_extended {
+    use super::*;
+
+    #[test]
+    fn test_rotate_east() {
+        let m = vec![
+            vec!['#', 'O', 'O'],
+            vec!['.', '#', 'O'],
+            vec!['.', '.', 'O'],
+        ];
+
+        assert_eq!(
+            rotate_east(m),
+            vec![
+                vec!['.', '.', '#'],
+                vec!['.', '#', 'O'],
+                vec!['O', 'O', 'O'],
+            ]
+        )
+    }
+}