From a053db4b9b5ac15b2c506616c278ea225607ec26 Mon Sep 17 00:00:00 2001
From: subcrip <contact@subc.rip>
Date: Wed, 24 Apr 2024 12:33:14 +0800
Subject: [PATCH] Update trees/quick_union.cc

Signed-off-by: subcrip <contact@subc.rip>
---
 trees/quick_union.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/trees/quick_union.cc b/trees/quick_union.cc
index 465654e..aea85b3 100644
--- a/trees/quick_union.cc
+++ b/trees/quick_union.cc
@@ -13,6 +13,7 @@ public:
     }
     
     void merge(size_t i, size_t j) {
+        if (connected(i, j)) return;
         sz[query(j)] += sz[query(i)];
         c[query(i)] = query(j);
     }