Задача на алгоритм Дейкстры

dijkstra_test.py

from collections import defaultdict


class Graph:
    def __init__(self):
        self.nodes = set()
        self.edges = defaultdict(list)
        self.distances = {}

    def add_node(self, value):
        self.nodes.add(value)

    def add_edge(self, from_node, to_node, distance1, distance2):
        self.edges[from_node].append(to_node)
        self.edges[to_node].append(from_node)
        self.distances[(from_node, to_node)] = distance1
        self.distances[(to_node, from_node)] = distance2


def dijkstra(graph, initial):
    visited = {initial: 0}

    nodes = set(graph.nodes)

    while nodes:
        min_node = None
        for node in nodes:
            if node in visited:
                if min_node is None:
                    min_node = node
                elif visited[node] < visited[min_node]:
                    min_node = node

        if min_node is None:
            break

        nodes.remove(min_node)
        current_weight = visited[min_node]

        for edge in graph.edges[min_node]:
            weight = current_weight + graph.distances[(min_node, edge)]
            if edge not in visited or weight < visited[edge]:
                visited[edge] = weight

    return visited

n = int(input())
roads = Graph()
for i in range(0, n):
    roads.add_node(i)

costs = [int(s) for s in input().split()]

m = int(input())
if m != 0:
    edges = [int(s) for s in input().split()]
    for j in range(0, 2 * m, 2):
        t1 = edges[j] - 1
        t2 = edges[j + 1] - 1

        roads.add_edge(t1, t2, costs[t1], costs[t2])

result = dijkstra(roads, 0)
if n - 1 in result:
    print(result[n - 1])
else:
    print(-1)