请写出改进Dijkstra算法的奖励机制和非完全贪心策略的算法代码
时间: 2023-06-12 13:04:24 浏览: 90
改进Dijkstra算法的奖励机制和非完全贪心策略可以用A*算法实现。A*算法基于Dijkstra算法,在Dijkstra算法的基础上增加了启发式函数,通过启发式函数的预估值来进行优化搜索。具体实现如下:
```python
def A_star(start, end, graph, heuristic):
# 初始化起点和终点的信息,包括距离和路径
distance = {node: float("inf") for node in graph}
distance[start] = 0
path = {start: []}
current_node = start
while current_node != end:
# 遍历当前节点的所有邻接节点,计算距离和启发式函数值
for neighbor in graph[current_node]:
# 计算该节点前往邻居节点的距离
tentative_distance = distance[current_node] + graph[current_node][neighbor]
if tentative_distance < distance[neighbor]:
# 更新当前路径和距离
distance[neighbor] = tentative_distance
path[neighbor] = path[current_node] + [current_node]
# 计算启发式函数值
f_score = tentative_distance + heuristic(neighbor, end)
# 将邻居节点加入开放列表
open_list.put((f_score, neighbor))
# 从开放列表中选择下一个节点
if not open_list.empty():
current_node = open_list.get()[1]
else:
# 如果开放列表为空则说明无法到达终点,直接返回
return "Path does not exist"
# 返回最短路径和距离
return path[end] + [end], distance[end]
```
其中,启发式函数可以根据具体情况进行设计。例如,对于地图搜索问题,可以将启发式函数设置为当前节点到终点的欧几里得距离。
在非完全贪心策略中,可以将每个节点的邻居节点按照一定的规则排序,先考虑距离较近的节点。具体实现如下:
```python
def non_greedy_dijkstra(start, end, graph):
# 初始化起点和终点的信息,包括距离和路径
distance = {node: float("inf") for node in graph}
distance[start] = 0
path = {start: []}
visited = []
current_node = start
while current_node != end:
# 遍历当前节点的所有邻接节点,并按照距离排序
sorted_neighbors = sorted(graph[current_node].items(), key=lambda x: x[1])
for neighbor, weight in sorted_neighbors:
# 计算该节点前往邻居节点的距离
tentative_distance = distance[current_node] + weight
if tentative_distance < distance[neighbor]:
# 更新当前路径和距离
distance[neighbor] = tentative_distance
path[neighbor] = path[current_node] + [current_node]
# 将当前节点加入已访问列表,并选择下一个节点
visited.append(current_node)
unvisited_neighbors = {node: distance[node] for node in graph if node not in visited}
if not unvisited_neighbors:
# 如果所有节点都已访问,则说明无法到达终点,直接返回
return "Path does not exist"
current_node = min(unvisited_neighbors, key=unvisited_neighbors.get)
# 返回最短路径和距离
return path[end] + [end], distance[end]
```
阅读全文