lingo最短路问题的路径约束代码
时间: 2023-10-16 15:17:23 浏览: 73
以下是使用Dijkstra算法解决Lingo最短路问题的Python代码示例,其中包含路径约束:
```python
import heapq
def dijkstra(graph, start, end, constraints):
dist = {v: float('inf') for v in graph}
dist[start] = 0
heap = [(0, start, [])]
while heap:
(d, u, path) = heapq.heappop(heap)
if d > dist[u]:
continue
path = path + [u]
if u == end:
return (dist[u], path)
for v, weight in graph[u].items():
if (u, v) in constraints or (v, u) in constraints:
continue
if dist[u] + weight < dist[v]:
dist[v] = dist[u] + weight
heapq.heappush(heap, (dist[v], v, path))
return (float('inf'), [])
graph = {
'A': {'B': 2, 'C': 3},
'B': {'D': 4, 'E': 2},
'C': {'F': 1},
'D': {'G': 1},
'E': {'G': 2},
'F': {'G': 3},
'G': {}
}
start = 'A'
end = 'G'
constraints = [('B', 'E')]
(distance, path) = dijkstra(graph, start, end, constraints)
print(distance)
print(path)
```
输出为:
```
7
['A', 'C', 'F', 'G']
```
其中,`graph`表示图的邻接矩阵,`start`表示起点,`end`表示终点,`constraints`表示路径约束,这里只有一条约束路径为'B'到'E'。`dijkstra`函数返回一个元组,第一个元素表示起点到终点的最短距离,第二个元素表示最短路径。在搜索过程中,如果当前节点和下一个节点形成的边在约束路径中,则跳过这个节点。