最小生成树算法将单词列表转换为问题图

Question

我一直在尝试从一个列表或单词串构建一个最小生成树的问题加权图，因为给定一个字符串到命名元组列表，单词的每个可能组合都是头部和尾部，并带有附加的头部“根”

输入：

['john', 'saw', 'mary', 'root']

要求的输出：

[Arc('root',weight,'saw'),Arc('root',weight,'john'),Arc('root', weight,'mary'),
 Arc('saw', weight,'john'), Arc('john', weight, 'saw'), Arc('saw', weight,'mary'),Arc('john', weight,'mary'),
 Arc('mary', weight,'john'),Arc('saw', weight,'mary'),Arc('mary', weight,'saw')]

码：

from collections import defaultdict, namedtuple 

Arc = namedtuple('Arc', ('head', 'weight', 'tail'))

def Constrain_graph(sentence):
    Arc = namedtuple('Arc', ('head', 'weight', 'tail'))
    C_graph=[]
    for wordindex in range(1, len(sentence)):
        G = nx.DiGraph()
        G.nodes(sentence[wordindex])

        #G.add_node(nod)
        G.add_nodes_from(range(1,len(sentence)))
        C_graph=nx.Graph()
    return C_graph

我需要输出如上所述