Added Dijkstra algorithm

SearchingAlgorithms/GraphSearch/dijkstra.py

@@ -0,0 +1,62 @@
+import heapq
+
+data = {
+    "Oradea": {"conn": [("Zerind", 71), ("Sibiu", 151)]}
+    ,"Zerind": {"conn": [("Oradea", 71), ("Arad", 75)]}
+    ,"Arad": {"conn": [("Zerind", 75), ("Sibiu", 140), ("Timisoara", 118)]}
+    ,"Timisoara": {"conn": [("Arad", 118), ("Lugoj", 111)]}
+    ,"Lugoj": {"conn": [("Timisoara", 111), ("Mehadia", 70)]}
+    ,"Mehadia": {"conn": [("Lugoj", 70), ("Drobeta", 75)]}
+    ,"Drobeta": {"conn": [("Mehadia", 75), ("Craiova", 120)]}
+    ,"Craiova": {"conn": [("Drobeta", 120), ("Rimnicu Vilcea", 146), ("Pitesti", 138)]}
+    ,"Sibiu": {"conn": [("Arad", 140), ("Oradea", 151), ("Fagaras", 99), ("Rimnicu Vilcea", 80)]}
+    ,"Fagaras": {"conn": [("Sibiu", 99), ("Bucharest", 211)]}
+    ,"Rimnicu Vilcea": {"conn": [("Sibiu", 80), ("Pitesti", 97), ("Craiova", 146)]}
+    ,"Pitesti": {"conn": [("Rimnicu Vilcea", 97), ("Craiova", 138), ("Bucharest", 101)]}
+    ,"Bucharest": {"conn": [("Pitesti", 101), ("Fagaras", 211), ("Giurgiu", 90), ("Urziceni", 85)]}
+    ,"Giurgiu": {"conn": [("Bucharest", 90)]}
+    ,"Urziceni": {"conn": [("Bucharest", 85), ("Hirsova", 98), ("Vaslui", 142)]}
+    ,"Hirsova": {"conn": [("Urziceni", 98), ("Eforie", 86)]}
+    ,"Eforie": {"conn": [("Hirsova", 86)]}
+    ,"Vaslui": {"conn": [("Urziceni", 142), ("Iasi", 92)]}
+    ,"Iasi": {"conn": [("Vaslui", 92), ("Neamt", 87)]}
+    ,"Neamt": {"conn": [("Iasi", 87)]}
+}
+
+def dijkstra(db, frm, to):
+    # Input sanity check
+    if frm is to or frm not in db or to not in db:
+        return []
+
+    # Init internal data structure
+    queue = []
+    heapq.heappush(queue, (0, (frm, [frm])))
+
+    # Set datastore objects to visited
+    selected = {frm: {"state": "start", "route": [frm], "dist": 0},
+                to: {"state": "goal", "route": [to], "dist": 0}}
+
+    # Start routing with two processes until reaching a common point
+    while queue:
+        # Get the vertex with the lowest distance (highest priority in the queue)
+        (dist, (location, route)) = heapq.heappop(queue)
+
+        # If the goal is found then return the route
+        if location in selected and selected[location]["state"] is "goal":
+            return {"dist": selected[location]["dist"] + dist,
+                    "route": route[:-1:] + selected[location]["route"][::-1]}
+        # If the vertex has not been visited yet add it to visited ones
+        elif location not in selected:
+            selected[location] = {"state": "visited", "route": route, "dist": dist}
+
+        # Take all connected vertices and add them to the queue
+        for (cLocation, cDist) in db[location]["conn"]:
+            # Check if vertex has already not yet been used
+            # Goal check is done since the goal is in selected from the beginning on
+            if cLocation not in selected or selected[cLocation]["state"] is "goal":
+                # Add to be processed later
+                heapq.heappush(queue, (dist + cDist, (cLocation, route + [cLocation])))
+
+    return {"error": "No route found!"}
+
+dijkstra(data, "Oradea", "Neamt")