From 2c51332c94653d59c231d4ae7b9147807356d6d3 Mon Sep 17 00:00:00 2001
From: Aleksandr Demakin <alexander.demakin@gmail.com>
Date: Mon, 9 Sep 2024 23:53:03 +0100
Subject: [PATCH] tree: optimise `findReplacement` used in deletion operation.

source: Russell A. Brown, Optimized Deletion From an AVL Tree.
https://arxiv.org/pdf/2406.05162v5.
---
 src/avl.zig | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/avl.zig b/src/avl.zig
index d409d28..1e27a26 100644
--- a/src/avl.zig
+++ b/src/avl.zig
@@ -599,16 +599,16 @@ pub fn TreeWithOptions(comptime K: type, comptime V: type, comptime Cmp: fn (a:
             const right = loc.child(.right);
             if (left) |l| {
                 if (right) |r| {
-                    if (l.data().h <= r.data().h) {
+                    // Russell A. Brown, Optimized Deletion From an AVL Tree.
+                    // https://arxiv.org/pdf/2406.05162v5
+                    if (loc.balance() <= 0) {
                         return goRight(l);
                     }
                     return goLeft(r);
                 }
-                return goRight(l);
-            } else if (right) |r| {
-                return goLeft(r);
+                return left;
             }
-            return null;
+            return right;
         }
 
         // getMin returns the minimum element of the tree.