From 88d691225e1d8a8968ce8df9c0f87bf9219458a5 Mon Sep 17 00:00:00 2001
From: Matej Focko <mfocko@redhat.com>
Date: Thu, 12 May 2022 12:20:55 +0200
Subject: [PATCH] chore(avl): refactor

Fixes #2

Signed-off-by: Matej Focko <mfocko@redhat.com>
---
 avl.py | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/avl.py b/avl.py
index 5a6c2b0..00f16b5 100644
--- a/avl.py
+++ b/avl.py
@@ -124,20 +124,17 @@ class AVLTree(RankedTree[T]):
 
         if rotating_around_root:
             self.root = new_root
-        return factor == 0
+        return factor != 0
 
     def __delete_fixup(
-        self, y: Optional[Node[T]], parent: Optional[Node[T]] = None
+        self, x: Optional[Node[T]], parent: Optional[Node[T]] = None
     ) -> bool:
-        x = y if y else parent
-        assert x
-
         factor = _balance_factor(x)
         if factor == 0:
             _update_rank(x)
-            return False
-        elif factor in (-1, 1):
             return True
+        elif factor in (-1, 1):
+            return False
 
         rotating_around_root = x.parent is None
         y, leaning, to_left, to_right = (
@@ -158,11 +155,13 @@ class AVLTree(RankedTree[T]):
     def _delete_rebalance(
         self, node: Optional[Node[T]], parent: Optional[Node[T]]
     ) -> None:
-        while node or parent:
-            # TODO: Check if it is possible to not propagate all the way up.
-            # if self.__delete_fixup(node, parent):
-            #     return
-            self.__delete_fixup(node, parent)
-            node, parent = parent, (parent.parent if parent else None)
+        if not node and not parent:
+            return
+
+        if not node:
+            node, parent = parent, parent.parent
+
+        while node and self.__delete_fixup(node, parent):
+            node, parent = parent, parent.parent if parent else None
 
     # endregion DeleteRebalance