From 4c9e7f28382980edc10eaee96ccddd4428678558 Mon Sep 17 00:00:00 2001
From: Stefan Harmuth <stefan.harmuth@docomodigital.com>
Date: Sun, 20 Dec 2020 20:23:26 +0100
Subject: [PATCH] day20: comment to clarify the == 4

---
 day20.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/day20.py b/day20.py
index 6693067..9f4a192 100644
--- a/day20.py
+++ b/day20.py
@@ -81,7 +81,7 @@ def getCornerPieces(tile_dict, only_get_first_piece=False):
         for border in tile.getPossibleBorderList():
             single_borders += all_borders.count(border) - 1
 
-        if single_borders == 4:
+        if single_borders == 4:  # every border shows up twice (1x straight, 1x reversed)
             if only_get_first_piece:
                 return tile_id
             corner_pieces.append(tile_id)