543. Diameter of Binary Tree

https://leetcode.com/problems/diameter-of-binary-tree/

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

Example:

Given a binary tree

1
         / \
        2   3
       / \     
      4   5    

Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

Note: The length of path between two nodes is represented by the number of edges between them.

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Similar problems
124-binary-tree-maximum-path-sum
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Intuition

At every recursive call, we want to return the longer path, so it is the best path to be combined with calling function
=> Return max (l, r) + 1 (for the edge to that node)

At every call, track global max path going through the node => l + r
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