[理工] [離散]-政大97
Let G be a planar graph with 30 vertices and 50 edges .Then
there are ? regions if G has 5 connected components?
答案
假設每個component 具點數Vi 邊數ei region個數ri , i=1,2,3,4,5
則 Vi-ei+ri =2
Σ (Vi-ei+ri) =10
因為v ＝ΣVi , e=Σei ,r= (Σ(ri-1)) +1 = (Σri)-4
我想請問上式 r= (Σ(ri-1)) +1 是怎麼來的
v-e+r =10-4 =6
so r=6-30+50=26
謝謝各位指教
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※ 編輯: bigrat2 來自: 114.41.112.218 (03/03 15:14)
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