Maximum Height Tree

Posted: 25 Jun, 2021
Difficulty: Hard

PROBLEM STATEMENT

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You are given a tree with ‘N’ nodes and ‘N-1’ edges. Your task is to determine the tree's maximum height when we consider any arbitrary node as a root.

For Example:
N = 4
Edges = [2 3], [4 3], [1 3]

Output: 2

Here node 4 is at a distance 2 from node 1 and if we make node 1 as a root, it will give the height of 2, which is the maximum possible in this tree.
Input Format:
The first line contains a single integer 'T' denoting the number of test cases to be run. Then the test cases follow.

The first line of each test contains integer 'N' denoting the number of nodes in the tree, and the following N-1 lines contain two nodes each.
Output Format:
For each test case, print an integer denoting the tree's maximum height when we consider any arbitrary node as a root. 
Note
You are not required to print anything; it has already been taken care of. Just implement the function.
Constraints:
1 <= T <= 50
1 <= N <= 10^4

Time Limit: 1 sec.
Approach 1

A straightforward approach would be to traverse the tree using DFS for every node and calculate the maximum height when the node is treated as the tree's root. The time complexity for the DFS traversal of a tree is O(N). The overall time complexity of DFS for all N nodes will be O(N^2).

 

Algorithm

  • Make one variable result to store the answer
  • Iterate over all nodes and call dfs function for each of the value
  • Make the dfs() function and run the function till we are not the last node of the subtree.
  • In the dfs() function we iterate on the adjacent nodes on the current node and call dfs() for them separately. And each dfs() function will return a variable mx which is max length path from that node.
  • Call dfs for each subtree of the root node and mark the max of the height of all nodes in a global variable result.
  • Return result


 

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