Create Dijkstra.py

GreedyAlgorithms/Dijkstra.py

@@ -0,0 +1,76 @@
+import sys 
+
+class Graph(): 
+
+    def __init__(self, vertices): 
+        self.V = vertices 
+        self.graph = [[0 for column in range(vertices)]  
+                      for row in range(vertices)] 
+
+    def printSolution(self, dist): 
+        print "Vertex tDistance from Source"
+        for node in range(self.V): 
+            print node, "t", dist[node] 
+
+    # A utility function to find the vertex with  
+    # minimum distance value, from the set of vertices  
+    # not yet included in shortest path tree 
+    def minDistance(self, dist, sptSet): 
+
+        # Initilaize minimum distance for next node 
+        min = sys.maxint 
+
+        # Search not nearest vertex not in the  
+        # shortest path tree 
+        for v in range(self.V): 
+            if dist[v] < min and sptSet[v] == False: 
+                min = dist[v] 
+                min_index = v 
+
+        return min_index 
+
+    # Funtion that implements Dijkstra's single source  
+    # shortest path algorithm for a graph represented  
+    # using adjacency matrix representation 
+    def dijkstra(self, src): 
+
+        dist = [sys.maxint] * self.V 
+        dist[src] = 0
+        sptSet = [False] * self.V 
+
+        for cout in range(self.V): 
+
+            # Pick the minimum distance vertex from  
+            # the set of vertices not yet processed.  
+            # u is always equal to src in first iteration 
+            u = self.minDistance(dist, sptSet) 
+
+            # Put the minimum distance vertex in the  
+            # shotest path tree 
+            sptSet[u] = True
+
+            # Update dist value of the adjacent vertices  
+            # of the picked vertex only if the current  
+            # distance is greater than new distance and 
+            # the vertex in not in the shotest path tree 
+            for v in range(self.V): 
+                if self.graph[u][v] > 0 and sptSet[v] == False and \ 
+                dist[v] > dist[u] + self.graph[u][v]: 
+                        dist[v] = dist[u] + self.graph[u][v] 
+
+        self.printSolution(dist) 
+
+# Driver program 
+g = Graph(9) 
+g.graph = [[0, 4, 0, 0, 0, 0, 0, 8, 0], 
+           [4, 0, 8, 0, 0, 0, 0, 11, 0], 
+           [0, 8, 0, 7, 0, 4, 0, 0, 2], 
+           [0, 0, 7, 0, 9, 14, 0, 0, 0], 
+           [0, 0, 0, 9, 0, 10, 0, 0, 0], 
+           [0, 0, 4, 14, 10, 0, 2, 0, 0], 
+           [0, 0, 0, 0, 0, 2, 0, 1, 6], 
+           [8, 11, 0, 0, 0, 0, 1, 0, 7], 
+           [0, 0, 2, 0, 0, 0, 6, 7, 0] 
+          ]; 
+
+g.dijkstra(0);