From fe405dd4778fece84c8eebd9e58b951cf34c0dcd Mon Sep 17 00:00:00 2001
From: Devon Sawatsky <devon@nove.dev>
Date: Fri, 05 Dec 2025 05:34:54 +0000
Subject: [PATCH] day5 part2

---
 src/day5.rs | 28 +++++++++++++++++++++++++++-
 src/lib.rs | 14 +++++++-------
 2 file(s) changed, 34 insertion(s)(+), 8 deletion(s)(-)

diff --git a/src/day5.rs b/src/day5.rs
--- a/src/day5.rs
+++ b/src/day5.rs
@@ -10,7 +10,33 @@
 }
 
 pub fn day5_part2(input: &str) -> String {
-    todo!()
+    let (mut ranges, _) = parse(input);
+    ranges.sort_by_key(|r| *r.start());
+    let collapsed = collapse(&ranges);
+    let total_range = collapsed
+        .into_iter()
+        .fold(0, |acc, elem| acc + (elem.end() - elem.start() + 1));
+    total_range.to_string()
+}
+
+/// ranges must be sorted
+fn collapse(ranges: &[RangeInclusive<i64>]) -> Vec<RangeInclusive<i64>> {
+    let mut collapsed = vec![];
+
+    let mut current_range = ranges[0].clone();
+    for range in ranges {
+        if range.start() <= current_range.end() {
+            if range.end() > current_range.end() {
+                current_range = *current_range.start()..=*range.end()
+            }
+        } else {
+            collapsed.push(current_range);
+            current_range = range.clone();
+        }
+    }
+    collapsed.push(current_range);
+
+    collapsed
 }
 
 fn parse(input: &str) -> (Vec<RangeInclusive<i64>>, Vec<i64>) {
diff --git a/src/lib.rs b/src/lib.rs
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -131,13 +131,13 @@
         let result = day5::day5_part1(include_str!("../input/day5.txt"));
         assert_eq!(result, "885");
     }
-    // #[test]
-    // fn day5_part2_test() {
-    //     let test_result = day5::day5_part2(include_str!("../input/day5.test.txt"));
-    //     assert_eq!(test_result, "43");
-    //     // let result = day5::day5_part2(include_str!("../input/day5.txt"));
-    //     // assert_eq!(result, "7922");
-    // }
+    #[test]
+    fn day5_part2_test() {
+        let test_result = day5::day5_part2(include_str!("../input/day5.test.txt"));
+        assert_eq!(test_result, "14");
+        let result = day5::day5_part2(include_str!("../input/day5.txt"));
+        assert_eq!(result, "348115621205535");
+    }
 
     #[test]
     fn day4_part1_test() {

--
tangled.sh