Python 實作Dijkstra算法_算法圖解

DijkstraAlgorithm

# 迪克斯特拉算法： 計算權重圖中的最短路徑
# graph: 起點start，a,b,終點fin之間的距離
graph = {}
graph["start"] = {}
graph["start"]["a"] = 6
graph["start"]["a"] = 2
graph["a"] = {}
graph["a"]["fin"] = 1
graph["b"] = {}
graph["b"]["a"] = 3
graph["b"]["fin"] = 5
graph["fin"] = {}
# costs: 起點到 a,b,fin的開銷
infinity = float("inf")
costs = {}
costs["a"] = 6
costs["b"] = 2
costs["fin"] = infinity
# parents： 存儲父節點，記錄最短路徑
parents = {}
parents["a"] = "start"
parents["b"] = "start"
parents["fin"] = None
# processed: 記錄處理過的節點，避免重複處理
processed = []

# find_lowest_cost_node(costs): 傳回開銷最低的點
def find_lowest_cost_node(costs):
    lowest_cost = float("inf")
    lowest_cost_node = None
    for node in costs:
        cost = costs[node]
        if cost < lowest_cost and node not in processed:
            lowest_cost = cost
            lowest_cost_node = node
    return lowest_cost_node


# Dijkstra implement
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)
 
print(processed)
           

output(win10+pthon 3.6)

windows下不能直接執行python檔案，跳轉到對應檔案夾後

python DijkstraAlgorithm.py

有向權重圖

結果