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["fin"] = 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
            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
            parents [n] = node
    processed.append(node)
    node = find_lowest_cost_node(costs)

path=["fin"]
p=parents["fin"]
while p!="start":
    path.insert(0, p)
    p=parents[p]
#
print("start", end="")
for p in path:
    print(f"=>{p}", end="")
path.insert(0, p)
print()
print(f"V={costs['fin']}")