From 1ccd8c0fb1d0b6b82ce37f3cd07ec540e7254791 Mon Sep 17 00:00:00 2001
From: Darkslayer3324j <nafayhassan3324j@gmail.com>
Date: Sat, 19 Sep 2026 21:22:47 +0500
Subject: [PATCH] Fix tree_sort dropping duplicate values

Node.insert ignored values equal to the current node, so
tree_sort([1, 1]) returned (1,). Send equal values to the right subtree and
add doctests for repeated values.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
---
 sorts/tree_sort.py | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/sorts/tree_sort.py b/sorts/tree_sort.py
index ffd339a31410..6c33d1109b93 100644
--- a/sorts/tree_sort.py
+++ b/sorts/tree_sort.py
@@ -36,11 +36,11 @@ def insert(self, val: T) -> None:
                 self.left = Node(val)
             else:
                 self.left.insert(val)
-        elif val > self.val:
-            if self.right is None:
-                self.right = Node(val)
-            else:
-                self.right.insert(val)
+        # Equal values go to the right so that duplicates are kept.
+        elif self.right is None:
+            self.right = Node(val)
+        else:
+            self.right.insert(val)
 
 
 def tree_sort[T: Comparable](arr: Iterable[T]) -> tuple[T, ...]:
@@ -63,6 +63,10 @@ def tree_sort[T: Comparable](arr: Iterable[T]) -> tuple[T, ...]:
     ('a', 'b', 'c')
     >>> tree_sort([2.5, -1, 0.0])
     (-1, 0.0, 2.5)
+    >>> tree_sort([3, 1, 3, 2, 1])
+    (1, 1, 2, 3, 3)
+    >>> tree_sort([2, 2, 2])
+    (2, 2, 2)
     >>> tree_sort([1, "a"])
     Traceback (most recent call last):
         ...