dijkstras-shortest-path-algorithm.py

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])
 
    def minDistance(self, dist, sptSet):
       min = sys.maxsize
 
        
        for u in range(self.V):
            if dist[u] < min and sptSet[u] == False:
                min = dist[u]
                min_index = u
 
        return min_index
 
  
    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)
 
 

if __name__ == "__main__":
    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)