day 25

src/day25.rs

@@ -1,18 +1,42 @@
 use aoc_runner_derive::{aoc, aoc_generator};
 
-type Input = ();
+type Input = (u64, u64);
 
-#[aoc_generator(day22)]
+#[aoc_generator(day25)]
 fn parse(input: &str) -> Input {
-    todo!()
+    let parts: Vec<&str> = input.split_whitespace().collect();
+    let row = parts[15].trim_end_matches(",").parse().unwrap();
+    let column = parts[17].trim_end_matches(".").parse().unwrap();
+
+    (column, row)
 }
 
-#[aoc(day22, part1)]
-fn part1(_: &Input) -> usize {
-    0
+#[aoc(day25, part1)]
+fn part1((col, row): &Input) -> u64 {
+    let diagonals_before = (col - 1) + (row - 1);
+    let entries_in_full_diags = (diagonals_before * diagonals_before + diagonals_before) / 2;
+    let target_diag_before = col - 1;
+
+    let entries_before_code = entries_in_full_diags + target_diag_before;
+    let mut val = 20151125;
+    for _ in 1..=entries_before_code {
+        val *= 252533;
+        val %= 33554393;
+    }
+    val
 }
 
-#[aoc(day22, part2)]
-fn part2(_: &Input) -> usize {
-    0
+#[aoc(day25, part2)]
+fn part2(_: &Input) -> &'static str {
+    "---"
+}
+
+#[cfg(test)]
+mod test {
+    use crate::day25::part1;
+
+    #[test]
+    fn foo() {
+        assert_eq!(21345942, part1(&(3, 4)));
+    }
 }

src/lib.rs

@@ -17,5 +17,6 @@ mod day21;
 mod day22;
 mod day23;
 mod day24;
+mod day25;
 
 aoc_lib! { year = 2015 }