LeetCode-in-All
543. Diameter of Binary Tree
Easy
Given the root of a binary tree, return 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.
The length of a path between two nodes is represented by the number of edges between them.
Example 1:
Input: root = [1,2,3,4,5]
Output: 3
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].
Example 2:
Input: root = [1,2]
Output: 1
Constraints:
- The number of nodes in the tree is in the range
[1, 104]. -100 <= Node.val <= 100
Solution
%% Definition for a binary tree node.
%%
%% -record(tree_node, {val = 0 :: integer(),
%% left = null :: 'null' | #tree_node{},
%% right = null :: 'null' | #tree_node{}}).
-spec diameter_of_binary_tree(Root :: #tree_node{} | null) -> integer().
depth(null) -> 0;
depth(Root) ->
1 + max(depth(Root#tree_node.left), depth(Root#tree_node.right)).
diameter_of_binary_tree(null) -> 0;
diameter_of_binary_tree(Root) ->
max(
max(
diameter_of_binary_tree(Root#tree_node.left),
diameter_of_binary_tree(Root#tree_node.right)
),
depth(Root#tree_node.left) + depth(Root#tree_node.right)
).