Python: Implement the Floyd-Warshall algorithm (all pairs shortest paths). — # Python Program for Floyd Warshall Algorithm V = 4 INF = 99999 def floydWarshall(graph): """ dist[][] will be the output matrix that will finally have the shortest distances between every pair of vertices """ """ initializing the solution matrix same as input graph matrix OR we can say that the initial values of shortest distances are based on shortest paths considerting no intermedidate vertices """ dist = map(lambda i : map(lambda j : j , i) , graph) """ Add all vertices one by one to the set of intermediate vertices. ---> Before start of a iteration, we have shortest distances between all pairs of vertices such that the shortest distances consider only the vertices in set {0, 1, 2, .. k-1} as intermediate vertices. ----> After the end of a iteration, vertex no. k is added to the set of intermediate vertices and the set becomes {0, 1, 2, .. k} """ for k in range(V): # pick all vertices as source one by one for i in range(V): # Pick all vertices as destination for the # above picked source for j in range(V): # If vertex k is on the shortest path from # i to j, then update the value of dist[i][j] dist[i][j] = min(dist[i][j] , dist[i][k]+ dist[k][j] ) printSolution(dist) def printSolution(dist): print "Following matrix shows the shortest distances\ between every pair of vertices" for i in range(V): for j in range(V): if(dist[i][j] == INF): print "%7s" %("INF"), else: print "%7d\t" %(dist[i][j]), if j == V-1: print "" """ 10 (0)------->(3) | /|\ 5 | | | | 1 \|/ | (1)------->(2) 3 """ graph = [[0,5,INF,10], [INF,0,3,INF], [INF, INF, 0, 1], [INF, INF, INF, 0] ] floydWarshall(graph); What does __getitem__ in a class allow us to use?,- iteration