def relax(self, u : _g.Vertex, v : _g.Vertex, weight):
'''
一步松弛操作
'''
if v.d > u.d + weight:
v.d = u.d + weight
v.pi = u
def initialize_single_source(self, g : _g.Graph, s : _g.Vertex):
'''
最短路径估计和前趋进行初始化 时间复杂度Θ(V)
'''
for v in g.veterxs:
v.d = _math.inf
v.pi = None
s.d = 0
