最小生成树和最短路径

盘荣博/图/例10.py

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+import networkx as nx
+import pylab as plt
+import numpy as np
+p=[25,26,28,31] ;a=[10,14,18,26] ; r=[20,16,13,11]
+b= np.zeros((5,5))
+
+for i in range(5):
+    for j in range(i+1,5):
+        b[i,j]=p[i]+np.sum(a[0:j-i])-r[j-i-1]
+G=nx.DiGraph(b)
+print(G)
+p=nx.dijkstra_path(G,source=0,target=4,weight='weight')
+print("最短路径为：",np.array(p)+1)#下标从零开始
+d=nx.dijkstra_path_length(G,source=0,target=4,weight="weight")
+print("所求的费用最小值为：",d)
+s=dict(zip(range(5),range(1,6)))
+plt.rc("font",size=16)
+pos=nx.shell_layout((G))#设置布局
+print(type(pos),'\npos=',pos)
+w=nx.get_edge_attributes(G,"weight")
+print(type(w),'\nw=',w)
+nx.draw(G,pos,font_weight='bold',labels=s,node_color='r')#绘制点和边
+nx.draw_networkx_edge_labels(G,pos,edge_labels=w)#绘制标签
+#绘制最短路径
+path_edges=list(zip(p,p[1:]))
+print(type(path_edges),"\npath_edges=",path_edges)
+nx.draw_networkx_edges(G,pos,edgelist=path_edges,edge_color="r",width=1)
+plt.savefig("figure10_9.png");plt.show()