给我christofides的python代码
时间: 2023-07-10 22:16:18 浏览: 44
以下是一个简单的Python实现Christofides算法的代码:
```python
import networkx as nx
from networkx.utils import pairwise
from collections import defaultdict
def christofides_tsp(G):
# 构建最小生成树
T = nx.minimum_spanning_tree(G)
# 找到所有奇度节点
odd_degree_nodes = [v for v, d in T.degree() if d % 2 == 1]
# 构建奇度节点之间的完美匹配
odd_degree_subgraph = G.subgraph(odd_degree_nodes)
matching = nx.algorithms.max_weight_matching(odd_degree_subgraph)
# 将匹配边添加到最小生成树中
for u, v in matching:
T.add_edge(u, v)
# 找到欧拉回路
eulerian_circuit = list(nx.eulerian_circuit(T))
# 去重
visited = defaultdict(lambda: False)
circuit = [eulerian_circuit[0][0]]
for u, v in eulerian_circuit:
if not visited[u]:
visited[u] = True
circuit.append(u)
if not visited[v]:
visited[v] = True
circuit.append(v)
# 计算TSP的近似解
return sum(G[u][v]['weight'] for u, v in pairwise(circuit))
```
这个实现使用了networkx库来进行图的操作和算法的计算。将一个带权无向图G作为输入,函数返回一个近似的TSP解。