PT07Z  Longest path in a tree
You are given an unweighted, undirected tree. Write a program to output the length of the longest path (from one node to another) in that tree. The length of a path in this case is number of edges we traverse from source to destination.
Input
The first line of the input file contains one integer N  number of nodes in the tree (0 < N <= 10000). Next N1 lines contain N1 edges of that tree  Each line contains a pair (u, v) means there is an edge between node u and node v (1 <= u, v <= N).
Output
Print the length of the longest path on one line.
Example
Input: 3 1 2 2 3 Output: 2
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avx_5801:
20210714 10:41:58
AC in One Go ...by using just 2 dfs call one call for finding farthest node and other for finding longest distances using farthest node :) 

darkdeveloper:
20210707 20:03:48
The question is highly misleading i tried a lot of times the actual number of nodes is greater than 10000. I took an array of 1e6 for the solution to finally get accepted. If your code fails at test(5) take the size of array to be 1e6 (1000000) 

loser_404:
20210604 08:15:42
useful lecture https://www.youtube.com/watch?v=JahlIiTzZWQ&t=947s&ab_channel=HiteshTripathiHiteshTripathi 

adi123cm:
20210602 03:49:54
use double dfs 

adi123cm:
20210602 03:49:29
good question helped clear my concepts. 

lolkey:
20210420 18:04:44
AC in one GO :)


rushi2001:
20210409 21:24:19
@wiseman_123  How can you say that space is O(1)


wiseman_123:
20210224 19:19:39
time  O(N).


wille_25:
20201230 13:17:44
AC in one GO


kapilsukrit2:
20200922 10:12:46
just use the diameter of a tree concept. you're good to go then! 
Added by:  ThanhVy Hua 
Date:  20070328 
Time limit:  0.5s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JSRHINO NODEJS PERL6 VB.NET 
Resource:  Coauthor Amber 