|
|
- # 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);
-
|
