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.


The first line of the input file contains one integer N --- number of nodes in the tree (0 < N <= 10000). Next N-1 lines contain N-1 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).


Print the length of the longest path on one line.


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rockstar_786: 2019-07-05 22:15:49

@sarthak_1998 bro i was getting the same its due to small memory allocation of declared array.
You are doing a mistake like this : ---->
int arr[2000][2000];
int a = arr[2001] [2000];

You can read one of the answers here.

an09mous: 2019-07-03 12:12:10

We can precompute heights of all the sub-trees in an array for faster computation

shahayush457: 2019-07-02 09:37:56

Just use 2 dfs :)

sarthak_1998: 2019-06-26 17:26:59

My code is giving runtime error (SIGSEGV) however it is giving right answer on every test case I tried. Please, someone, help me.

anand_undavia: 2019-06-15 19:27:03

This helped me a lot:

Also, SPOJtoolkit has really nice test cases for this problem -- apart from well, the first test case.

cenation007: 2019-06-03 17:01:17

take any node as root, start with root to find longest path
and the rest is dfs
AC in one go:)

Last edit: 2019-06-03 17:01:56
arunkumarreddy: 2019-06-02 20:16:54

i have submitted solutions for 2 problems on graphs today. I got NZEC error for both the problems, can someone help me understand why i am getting that error. If you want i can share my code with you.

klmo: 2019-04-25 15:38:38

1 DFS. finally ac in java.

klmo: 2019-04-25 13:45:49

2 dfs operation with tree in adjacency matrix is giving TLE in java. Using BufferedReader. Any suggestion?

brijraj: 2019-02-17 11:54:05

@suvro_coder your input is wrong. There are 7 nodes instead of 6. Otherwise it will not add edge from 6 to 7

Added by:Thanh-Vy Hua
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Memory limit:1536MB
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