Реализация алгоритма Форда-Беллмана

class Graph:
 
    def __init__(self, vertices):
        self.vertices = vertices
        self.graph = []
 
    def addEdge(self, a, b, weight):
        self.graph.append([a, b, weight])
 
    def printAnswer(self, distance):
        for i in range(self.vertices):
            print("{0}\t\t{1}".format(i, distance[i]))
 
    def bellmanFord(self, src):
 
        distance = [float("Inf")] * self.vertices
        distance[src] = 0
 
        for i in range(self.vertices - 1):
 
            for a, b, weight in self.graph:
                 if distance[a] != float("Inf") and distance[a] + weight < distance[b]:
                    distance[b] = distance[a] + weight
       
 
 
 
 
        for a, b, weight in self.graph:
            if distance[a] != float("Inf") and distance[a] + weight < distance[b]:
                print("Graph contains negative weight cycle")
                return None
        self.printAnswer(distance)
        return distance
 
 
 
g = Graph(5)
g.addEdge(0, 1, -1)
g.addEdge(0, 2, 4)
g.addEdge(1, 2, 3)
g.addEdge(1, 3, 2)
g.addEdge(1, 4, 2)
g.addEdge(3, 2, 5)
g.addEdge(3, 1, 1)
g.addEdge(4, 3, -3)
print(g.bellmanFord(0))