圍長 (圖論)
籠 (Cage)
最小的圍長為 g 的三次圖(3-正則圖)稱做 g-籠(或是 (3,g)-籠)。彼得森你圖是唯一的 5-籠,Heawood graph 則是唯一的 6-籠,McGee graph 是唯一的 7-籠,Tutte eight cage 是唯一的 8-籠。[3] 對特定的圍長來說,可能會存在不只一個籠。比如,存在三個不同構的 10-籠,分別都有 70 條邊:Balaban 10-cage、Harries graph、Harries–Wong graph。
- The Petersen graph has a girth of 5
- The Heawood graph has a girth of 6
- The McGee graph has a girth of 7
- The Tutte–Coxeter graph (Tutte eight cage) has a girth of 8
參考文獻
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