diff --git a/graphs/dijkstra.py b/graphs/dijkstra.py
index 6b08b28fc..4b6bc347b 100644
--- a/graphs/dijkstra.py
+++ b/graphs/dijkstra.py
@@ -20,12 +20,12 @@ import heapq
 
 def dijkstra(graph, start, end):
     heap = [(0, start)]  # cost from start node,end node
-    visited = []
+    visited = set()
     while heap:
         (cost, u) = heapq.heappop(heap)
         if u in visited:
             continue
-        visited.append(u)
+        visited.add(u)
         if u == end:
             return cost
         for v, c in G[u]: