谁能用python这个求最大流最小割程序啊,我有一段程序,里面急需假如这个最大流最小割,有没有人会?
使用 Python 来实现最大流最小割算法。下面是一个使用 Python 实现 Ford-Fulkerson 算法的例子,可以求解有向图的最大流量:
# Ford-Fulkerson Algorithm (Edmonds-Karp Algorithm)
# Uses Breadth First Search to find augmenting paths
from collections import deque
def bfs(graph, source, sink, parent):
# Create a visited array and mark all vertices as not visited
visited = [False] * len(graph)
# Create a queue and enqueue the source node
queue = deque()
queue.append(source)
visited[source] = True
while queue:
# Dequeue a vertex from the queue
u = queue.popleft()
# Get all adjacent vertices of the dequeued vertex u
for v, capacity in enumerate(graph[u]):
if visited[v] == False and capacity > 0:
# If the capacity is greater than zero and the vertex has not been visited,
# then mark it as visited and enqueue it
visited[v] = True
queue.append(v)
parent[v] = u
# If we can reach the sink node in BFS starting from the source node,
# then return True, else False
return visited[sink]
def ford_fulkerson_algorithm(graph, source, sink):
# Copy the original graph into a residual graph
residual_graph = [row[:] for row in graph]
# This array is filled by BFS and to store path
parent = [-1] * len(graph)
max_flow = 0 # Initialize the maximum flow
# Augment the flow while there is path from source to sink
while bfs(residual_graph, source, sink, parent):
# Find the path flow capacity
path_flow = float("Inf")
s = sink
while s != source:
path_flow = min(path_flow, residual_graph[parent[s]][s])
s = parent[s]
# Add path flow to overall flow
max_flow += path_flow
# Update residual capacities of the edges and reverse edges along the path
v = sink
while v != source:
u = parent[v]
residual_graph[u][v] -= path_flow
residual_graph[v][u] += path_flow
v = parent[v]
return max_flow
# Example Usage
graph = [[0, 16, 13, 0, 0, 0],
[0, 0, 10, 12, 0, 0],
[0, 4, 0, 0, 14, 0],
[0, 0, 9, 0, 0, 20],
[0, 0, 0, 7, 0, 4],
[0, 0, 0, 0, 0, 0]]
source = 0
sink = 5
max_flow = ford_fulkerson_algorithm(graph, source, sink)
print("Maximum Flow:", max_flow)
在这个例子中,我们使用了一个邻接矩阵来表示有向图,其中 graph[i][j]
表示从节点 i
到节点 j
的最大容量。使用 Ford-Fulkerson 算法计算最大流量时,我们首先复制一份原始的邻接矩阵,称之为残余图。然后我们使用 BFS 算法来查找增广路径,通过增加路径上最小容量的边来增加流量。在每次找到增广路径后,我们更新残余图中所有路径上的边的容量。如果没有增广路径可以继续优化,则算法结束,此时残余图中的边的容量即为最大流量。
当然,这只是其中一种算法的实现,不同的算法实现可能会有所不同。希望对你有所帮助!