Diameter of Binary Tree

LeetCode Q 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: input:[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.

Solution:

Code:

int res = 0;
public int diameterOfBinaryTree(TreeNode root) {
  if (root == null) return 0;
  dfs(root);
  return res;
}

private int dfs(TreeNode n) {
  if (n == null) return 0;
  int left = dfs(n.left), right = dfs(n.right);
  res = Math.max(res, left + right);
  return Math.max(left, right) + 1;
}