LeetCode 543 Diameter of Binary Tree - Algorithm

$1.$ Base case: if node is null, return height $0$.

$2.$ Recursively compute left height and right height.

$3.$ Diameter through this node = left height + right height. Update global max.

$4.$ Return $1$ + max(left height, right height) as this node's height.

Time: $O(n)$, visiting each node once. Space: $O(h)$ for recursion stack where $h$ is height. The recursion naturally handles the tree structure.