advent_of_code_2025

commit 3aa4adb519229ec0d4751a15e3e77467a55d4324
parent 2dcde482dafa08128e47e430679d868ad4a5361f
Author: Eamon Caddigan <ec@eamoncaddigan.net>
Date:   Fri,  5 Dec 2025 14:30:06 -0800

Solve day 05, part 2

Diffstat:
M
src/day05.R
 | 
34
++++++++++++++++++++++++++++++++++

1 file changed, 34 insertions(+), 0 deletions(-)
diff --git a/src/day05.R b/src/day05.R
@@ -66,9 +66,43 @@ test_part1 <- function() {
   stopifnot(part1(test_input) == 3)
 }
 
+count_fresh_ids <- function(fresh_ranges) {
+  add_remaining_fresh_ids <- function(row_id, last_fresh_id) {
+    new_ids <- if (fresh_ranges[row_id, 2] <= last_fresh_id) {
+      0
+    } else if (fresh_ranges[row_id, 1] <= last_fresh_id) {
+      fresh_ranges[row_id, 2] - last_fresh_id
+    } else {
+      fresh_ranges[row_id, 2] - fresh_ranges[row_id, 1] + 1
+    }
+
+    if (row_id == nrow(fresh_ranges)) {
+      new_ids
+    } else {
+      new_ids +
+        add_remaining_fresh_ids(
+          row_id + 1,
+          max(last_fresh_id, fresh_ranges[row_id, 2])
+        )
+    }
+  }
+  add_remaining_fresh_ids(1, 0)
+}
+
+part2 <- function(input_lines) {
+  input_parsed <- parse_input(input_lines)
+  count_fresh_ids(input_parsed$fresh_ranges)
+}
+
+test_part2 <- function() {
+  part2(test_input) == 14
+}
+
 main <- function() {
   test_part1()
   cat("Part 1 solution: ", part1(puzzle_input), "\n")
+  test_part2()
+  cat(sprintf("Part 2 solution: %0.0f\n", part2(puzzle_input)))
 }
 
 main()