Find the diameter of a binary tree

Question

I am trying to find the diameter of a binary tree (Path length between any two nodes in the tree containing maximum number of nodes.) in java.

my code snippet:

Answer 1

Algo takes O(n). Calculates height and path at the same time.

public static int findLongestPath(TreeNode root)
{
  // longest path = max (h1 + h2 + 2, longestpath(left), longestpath(right);

  int[] treeInfo = longestPathHelper(root);

  return treeInfo[0];
}

private static int[] longestPathHelper(TreeNode root)
{
  int[] retVal = new int[2];

  if (root == null)
  {
     //height and longest path are 0
     retVal[0] = 0;
     retVal[1] = 0;
  }

  int[] leftInfo = longestPathHelper(root.getLeft());
  int[] rightInfo = longestPathHelper(root.getRight());

  retVal[0] = Math.max(leftInfo[1] + rightInfo[1] + 2, Math.max(leftInfo[0], rightInfo[0]));
  retVal[1] = Math.max(leftInfo[1], rightInfo[1]) + 1;

  return retVal;
}