Day 20

Author: prevostc

README.md

@@ -30,9 +30,9 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 17](./src/bin/17.rs) | `1.7µs` | `361.3µs` |
 | [Day 18](./src/bin/18.rs) | `49.6µs` | `58.9µs` |
 | [Day 19](./src/bin/19.rs) | `204.0µs` | `693.5µs` |
-| [Day 20](./src/bin/20.rs) | `325.0µs` | `4.6ms` |
+| [Day 20](./src/bin/20.rs) | `307.5µs` | `1.8ms` |
 
-**Total: 19.39ms**
+**Total: 16.57ms**
 <!--- benchmarking table --->
 
 ---

src/bin/20.rs

@@ -49,6 +49,9 @@ fn dijkstra(grid: &Grid<char>, start: Point, end: Point) -> Grid<i64> {
 }
 
 fn solve<const CHEAT_MOVES: isize>(input: &str, min_gain: i64) -> Option<i64> {
+    assert!(CHEAT_MOVES > 1);
+    assert!(min_gain > 0);
+
     let (grid, start, end) = parse_input(input);
     let cost = dijkstra(&grid, start, end);
 
@@ -76,7 +79,6 @@ fn solve<const CHEAT_MOVES: isize>(input: &str, min_gain: i64) -> Option<i64> {
                 .map(|&(diff, moves)| (start_pos + diff, moves))
                 .filter(|&(pos, _)| cost.is_in_bounds(pos))
                 .filter(|&(pos, _)| cost[pos] != i64::MAX)
-                .filter(|&(pos, moves)| cost[pos] > start_cost + moves as i64)
                 .filter(|&(pos, moves)| cost[pos] - (start_cost + moves as i64) >= min_gain)
                 .count() as i64;
 
@@ -101,7 +103,7 @@ mod tests {
     #[test]
     fn test_part_one_0() {
         let input = advent_of_code::template::read_file("examples", DAY);
-        let result = solve::<2>(&input, 0);
+        let result = solve::<2>(&input, 1);
         assert_eq!(result, Some(44));
     }