Update day 18 solution

day-18/day-18.py

@@ -138,10 +138,10 @@ def part_1(input):
 
 def part_2(input):
     result = 0
-    nbrs = []
+    nbrs = set()
     for line in input:
         line = line.rstrip()
-        nbrs.append(parse(line))
+        nbrs.add(parse(line))
     for n1 in nbrs:
         for n2 in nbrs:
             if n1 == n2: