"""

543. Diameter of Binary Tree

https://leetcode.com/problems/diameter-of-binary-tree/#/description

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.

"""


# Definition for a binary tree node.
class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution(object):
    def __init__(self):
        self.max = 0
    
    def diameterOfBinaryTree(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if not root:
            return 0
        
        self.depth(root)
        
        return self.max
        
        
    def depth(self, node):
        
        if not node:
            return 0
        
        left = self.depth(node.left)
        right = self.depth(node.right)
        
        self.max = max ( self.max, left + right )
        
        return 1 + max( left, right )
        
        
    
    
def main():
    
    solution = Solution()
    
    root = TreeNode(0)
    root.left = TreeNode(1)
    root.left.left = TreeNode(2)
    root.left.left.left = TreeNode(3)
    root.left.left.left.left = TreeNode(4)
    
    root.left.right = TreeNode(5)
    root.left.right.right = TreeNode(6)
    root.left.right.right.right = TreeNode(7)
    
    root.right = TreeNode(8)
    

    
    print ( "6 == " + str ( solution.diameterOfBinaryTree(root) ))


if __name__ == '__main__':
    main()












