[問題] 用induction證明無向圖必有一點為non-cut

看板Prob_Solve (計算數學 Problem Solving)作者 (part2)時間11年前 (2013/10/30 21:14), 編輯推噓4(404)
留言8則, 3人參與, 最新討論串1/4 (看更多)
For an undirected graph G=(V, E) and a vertex v in V, let G\v denote the subgraph of G obtained by removing v and all the edges incident to v from G. If G is connected, then G\v can be connected or disconnected. Prove that for any connected graph G, we can always find a vertex v in G such that G\v is connected. 目前我的想法是1)沒有迴圈:視為樹,leaf必定是non-cut 2)有迴圈:有迴圈的話,degree不是最大的應該都可以是non-cut? 請問一下,我的觀念是否有錯? 還有如何用數學歸納法證明呢? -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 1.160.42.4

10/30 23:40, , 1F
_△∠ 左邊應該是你的 2) 的反例: deg 3 那點拿掉照斷
10/30 23:40, 1F

10/31 06:27, , 2F
2) 點雙連結?
10/31 06:27, 2F

10/31 06:28, , 3F
啊…沒事
10/31 06:28, 3F

11/03 17:01, , 4F
若是沒有 cycle 的話,找一條最長的 path,它的兩個端點
11/03 17:01, 4F

11/03 17:02, , 5F
都是 non-cut。就算是有 cycle,似乎也是如此。
11/03 17:02, 5F

11/04 09:27, , 6F
證明應該很簡單,最長的 path 的端與不在 path 上的點
11/04 09:27, 6F

11/04 09:27, , 7F
一定不相鄰,不然該 path 就不是最長的,所以是 non-cut
11/04 09:27, 7F

11/04 09:33, , 8F
所謂的最長應該是 maximal length、不是 maximum length
11/04 09:33, 8F
文章代碼(AID): #1ISGOXB1 (Prob_Solve)
文章代碼(AID): #1ISGOXB1 (Prob_Solve)