I found it in some paper ;) Diameter and center De nition 4. The diameter of tree is the length of the longest path. De nition 5. A center is a vertex v such that the longest path from v to a leaf is minimal over all vertices in the tree.Tree center(s) can be found using simple algorithm. Algorithm 1. (Centers of tree) 1: Choose a random root r. 2: Find a vertex v1 | the farthest form r. 3: Find a vertex v2 | the farthest form v1. 4: Diameter is a length of path from v1 to v2. 5: Center is a median element(s) of path from v1 to v2.
This is O(n) algorithm. It is clear that we can't determine tree isomorphism faster than O(n). So, if we nd a O(f(n)) algorithm for rooted trees isomorphism we can also obtain O(f(n)) algorithm for ordinary trees. On Saturday, June 16, 2012 12:04:32 PM UTC+5:30, achala sharma wrote: > > I think this algorithm is used for calculating poset in graph. > > On Sat, Jun 16, 2012 at 3:04 AM, Hemesh Singh <hemesh.mn...@gmail.com>wrote: > >> + 1 for DK's solution. Is that a standard algorithm coz I feel like I >> have heard it somewhere ?? >> >> >> On Mon, Aug 8, 2011 at 1:37 AM, DK <divyekap...@gmail.com> wrote: >> >>> @KK: DFS and BFS are O(N) and Floyd Warshall is O(N^3). >>> Could you please state how you can use the traversals directly to get >>> the center? (And prove your correctness too?) >>> >>> The solution given by Wladimir (& expanded upon by me) is O(N) and uses >>> (somewhat) the inverse of a BFS as a traversal. >>> >>> -- >>> DK >>> >>> http://twitter.com/divyekapoor >>> http://gplus.to/divyekapoor >>> http://www.divye.in >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Algorithm Geeks" group. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msg/algogeeks/-/HnMOZtOrkqwJ. >>> >>> To post to this group, send email to algogeeks@googlegroups.com. >>> To unsubscribe from this group, send email to >>> algogeeks+unsubscr...@googlegroups.com. >>> For more options, visit this group at >>> http://groups.google.com/group/algogeeks?hl=en. >>> >> >> >> >> -- >> Hemesh singh >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Algorithm Geeks" group. >> To post to this group, send email to algogeeks@googlegroups.com. >> To unsubscribe from this group, send email to >> algogeeks+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/algogeeks?hl=en. >> > > -- You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To view this discussion on the web visit https://groups.google.com/d/msg/algogeeks/-/BWplK7bCatMJ. To post to this group, send email to algogeeks@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
