deykstra.py

graph={}
graph["start"] = {}
graph["start"]["a"] = 6
graph["start"]["b"] = 2
graph["a"] = {}
graph["a"]["fin"]=1
graph["b"] = {}
graph["b"]["a"] = 3
graph["b"]["fin"]=5
graph["fin"] = {}



infinity = float("inf")
costs = {}
costs["a"] =6
costs["b"]= 2
costs["fin"]= infinity

parents = {}
parents["a"] = "start"
parents["b"] = "start"
parents["in"] = None


processed = []

def find_lowest_cost_node(costs):
    lowest_cost = float("inf")
    lowest_cost_node = None
    for node in costs:# Перебрать все узлы
        cost = costs[node]
        if cost < lowest_cost and node not in processed:
            lowest_cost = cost #он назначается новым
            lowest_cost_node = node
    return lowest_cost_node


node = find_lowest_cost_node(costs)
while node is not None:
    cost = costs[node]
    neighbors = graph[node]
    for n in neighbors.keys():
        new_cost = cost + neighbors[n]
        if costs[n]> new_cost:
            costs[n] = new_cost #обновить стоимо сть для этого узла
            parents [n] = node #" . · Этот узел становится новым родителем для соседа
    processed.append(node) #" . Узел помечается как обработанный
    node = find_lowest_cost_node (costs)

print(costs['fin'])

print(parents)