From 243a6b9e44485b8845d5fb2f2241a10cce419450 Mon Sep 17 00:00:00 2001
From: Joshua Young <djry1999@gmail.com>
Date: Sun, 25 Aug 2024 09:03:12 +1000
Subject: [PATCH] fix RedBlackTree::LeafNode-s being marked red

---
 CHANGELOG.md          |  1 +
 lib/red-black-tree.rb | 12 +++++++-----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 121b930..d19dd51 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## [Unreleased]
 
+- Fix `RedBlackTree::LeafNode`s being marked red
 - Handle comparison with `RedBlackTree::LeafNode` in subclasses of `RedBlackTreeNode`
 - Add `RedBlackTree#include?`
 - Add `RedBlackTree#search`
diff --git a/lib/red-black-tree.rb b/lib/red-black-tree.rb
index 8225fc7..1bab1ed 100644
--- a/lib/red-black-tree.rb
+++ b/lib/red-black-tree.rb
@@ -182,9 +182,11 @@ def delete! node
           end
 
           if node.distant_nephew && node.distant_nephew.valid? && node.distant_nephew.red?
-            case node.parent.colour
-            when Node::RED then node.sibling.red!
-            when Node::BLACK then node.sibling.black!
+            unless node.sibling.leaf?
+              case node.parent.colour
+              when Node::RED then node.sibling.red!
+              when Node::BLACK then node.sibling.black!
+              end
             end
             node.parent.black!
             node.distant_nephew.black!
@@ -194,7 +196,7 @@ def delete! node
           end
 
           if node.close_nephew && node.close_nephew.valid? && node.close_nephew.red?
-            node.sibling.red!
+            node.sibling.red! unless node.sibling.leaf?
             node.close_nephew.black!
             rotate_sub_tree! node.sibling, opp_direction
 
@@ -202,7 +204,7 @@ def delete! node
           end
 
           if node.parent.red?
-            node.sibling.red!
+            node.sibling.red! unless node.sibling.leaf?
             node.parent.black!
 
             break