Merge pull request #1545 from TheDesTrucToRR/master

Dijkstra algorithm for shortest path in weighted graph #458

Author: keshavsingh3197

Python/shortestpathWeightedGraph.py

@@ -0,0 +1,94 @@
+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):
+ 
+        # Initialize minimum distance for next node
+        min = sys.maxsize
+ 
+        # Search not nearest vertex not in the
+        # shortest path tree
+        for u in range(self.V):
+            if dist[u] < min and sptSet[u] == False:
+                min = dist[u]
+                min_index = u
+ 
+        return min_index
+ 
+    # Function that implements Dijkstra's single source
+    # shortest path algorithm for a graph represented
+    # using adjacency matrix representation
+    def dijkstra(self, src):
+ 
+        dist = [sys.maxsize] * 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.
+            # x is always equal to src in first iteration
+            x = self.minDistance(dist, sptSet)
+ 
+            # Put the minimum distance vertex in the
+            # shortest path tree
+            sptSet[x] = 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 shortest path tree
+            for y in range(self.V):
+                if self.graph[x][y] > 0 and sptSet[y] == False and \
+                dist[y] > dist[x] + self.graph[x][y]:
+                        dist[y] = dist[x] + self.graph[x][y]
+ 
+        self.printSolution(dist)
+ 
+# Driver program
+v = int(input("Enter total vertices in weighted graph : "))
+g = Graph(v)
+print("By default no vertex is connected to any vertex.If u want to connect any vertex to another then enter the index of both vertex one by one and then weight between them\nNote:Vertex index start from 0")
+
+while 1:
+    a = int(input("Enter first vertex:"))
+    b = int(input("Enter another vertex:"))
+    w =int(input("Enter weight:"))
+    g.graph[a][b] = g.graph[b][a] = w
+    c = input("Wanna connect another Y/N :")
+    if(c == "N" or c == "n"):
+        break
+    
+print("Graph :\n" , g.graph)
+    
+"""
+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]
+        ];
+"""
+print("above 2D array represent graph with row and columns index as connecting vertices and value as weight.0 value means that that vetices not connected.")
+s = int(input("Enter source vertex: "))
+
+g.dijkstra(a)