Merge pull request #23 from vipulSharma18/issue-#1-python-algorithms-vipulSharma18

Create Dijkstra.py

other/Dijkstra.py

@@ -0,0 +1,82 @@
+# Python program for Dijkstra's single 
+# source shortest path algorithm. The program is 
+# for adjacency matrix representation of the graph 
+
+# Library for INT_MAX 
+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); 
+