這是我爲圖形着色程序創建coalesce函數的嘗試。但是,它不適用於加權邊緣。
import networkx as nx
# G is a graph created using nx
# this is to establish the number of colors
k = 5
# inputs node1 and node2 are labels of nodes, e.g. 'a' or 'b' etc.
def coalesce(G,node1,node2):
"""Performs Briggs coalescing. Takes in the graph and two nodes.
Returns 1 if unable to coalesce, 0 otherwise."""
if node1 in G.neighbors(node2) or node2 in G.neighbors(node1):
print "Cannot coalesce. Node",node1,"and node",node2,"share an edge"
return 1
elif G.degree(node1)+G.degree(node2) >= k:
print "Cannot coalesce. Combined degree of",node1,"and",node2,"\
is",G.degree(node1)+G.degree(node2),"which is too high for k =",k
return 1
else:
newedge = []
for i in range(len(G.neighbors(node2))):
newedge.append((node1 , G.neighbors(node2)[i]))
G.add_edges_from(newedge)
G.remove_node(node2)
nx.relabel_nodes(G, {node1:node1+node2},copy=False)
return 0