543. 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.

# @lc code=start
using LeetCode

function diameter_of_binary_tree(root::TreeNode)::Int
    return max(
        diameter_of_binary_tree(root.left),
        diameter_of_binary_tree(root.right),
        _max_depth_to_leaf(root.left) + _max_depth_to_leaf(root.right) + 1,
    ) - 1
end

diameter_of_binary_tree(root::Nothing) = 0

function _max_depth_to_leaf(root::TreeNode)
    return max(1 + _max_depth_to_leaf(root.left), 1 + _max_depth_to_leaf(root.right))
end

_max_depth_to_leaf(::Nothing) = 0
# @lc code=end

_max_depth_to_leaf (generic function with 2 methods)

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