From 2ce82421c218ce45560746fdc0bf1e43c9925ded Mon Sep 17 00:00:00 2001
From: timeshifter <timeshifter@sumatrae>
Date: Thu, 2 Jul 2026 21:59:24 +0200
Subject: [PATCH] add day 20 part 2

---
 day20/src/main.rs | 41 +++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/day20/src/main.rs b/day20/src/main.rs
index 9d76a26..7ad0b7c 100644
--- a/day20/src/main.rs
+++ b/day20/src/main.rs
@@ -17,33 +17,34 @@ fn main() {
         })
         .collect();
 
-    // dbg!(&ranges);
-    let result = consolidate_all_ranges(&ranges);
-    dbg!(result);
+    let mut result = consolidate_all_ranges(&ranges);
+
+    result.sort_by_key(|r| *r.start());
+
+    println!("{}", result[0].end() + 1);
+    println!("{}", result.len() - 1);
 }
 
 fn consolidate_all_ranges(ranges: &[RangeInclusive<usize>]) -> Vec<RangeInclusive<usize>> {
     let mut work = ranges.to_vec();
 
-    let mut to_remove = (0, 0);
+    let mut found;
+    let mut to_remove;
+
     loop {
-        let mut found = None;
-        'middle: loop {
-            if work.len() == 1 {
-                break;
-            }
-            for i in 0..work.len() - 1 {
-                for j in i + 1..work.len() {
-                    if let Some(range) = merge_two_ranges(&[ranges[i].clone(), ranges[j].clone()]) {
-                        found = Some(range);
-                        to_remove = (i, j);
-                        break 'middle;
-                    }
+        found = None;
+        to_remove = (0, 0);
+
+        'inner: for i in 0..work.len() - 1 {
+            for j in i + 1..work.len() {
+                if let Some(range) = merge_two_ranges(&[work[i].clone(), work[j].clone()]) {
+                    found = Some(range);
+                    to_remove = (i, j);
+                    break 'inner;
                 }
             }
         }
         if let Some(range) = found {
-            dbg!(&range);
             work.remove(to_remove.1);
             work.remove(to_remove.0);
             work.push(range);
@@ -59,7 +60,7 @@ fn merge_two_ranges(ranges: &[RangeInclusive<usize>]) -> Option<RangeInclusive<u
     let a = &ranges[0];
     let b = &ranges[1];
 
-    if ranges_overlap(a, b) {
+    if ranges_overlap(a, b) || ranges_are_adjacent(a, b) {
         let start = if a.start() < b.start() {
             a.start()
         } else {
@@ -72,6 +73,10 @@ fn merge_two_ranges(ranges: &[RangeInclusive<usize>]) -> Option<RangeInclusive<u
     }
 }
 
+fn ranges_are_adjacent(a: &RangeInclusive<usize>, b: &RangeInclusive<usize>) -> bool {
+    *a.start() == b.end() + 1 || *b.start() == a.end() + 1
+}
+
 fn ranges_overlap(a: &RangeInclusive<usize>, b: &RangeInclusive<usize>) -> bool {
     (a.start() < b.start() && a.end() > b.start())
         || (b.start() < a.start() && b.end() > a.start())