Find Longest Path Between Two Nodes of a Tree in Python

Suppose we have a binary tree; we have to find the longest path between any two nodes in the tree.

So, if the input is like

 then the output will be 5 

To solve this, we will follow these steps:

• ans := 0

• Define a function getMaxPath() . This will take node

• if node is null, then

  • return 0

• leftCnt := getMaxPath(left of node)

• rightCnt := getMaxPath(right of node)

• temp := 1 + maximum of leftCnt and rightCnt

• ans := maximum of ans and l+r+1

• From the main method do the following −

• getMaxPath(root)

• return ans

Let us see the following implementation to get better understanding −

Example

 Live Demo

class TreeNode:
   def __init__(self, val, left=None, right=None):
      self.val = val
      self.left = left
      self.right = right

class Solution:
   def solve(self, root):
      self.ans = 0
      def getMaxPath(root):
         if root is None:
            return 0
         l = getMaxPath(root.left)
         r = getMaxPath(root.right)
         temp = max(l, r) + 1
         self.ans = max(self.ans, l + r + 1)
         return temp
      getMaxPath(root)
      return self.ans
ob = Solution()
root = TreeNode(2)
root.left = TreeNode(10)
root.right = TreeNode(4)
root.right.left = TreeNode(8)
root.right.right = TreeNode(2)
root.right.left.left = TreeNode(6)
print(ob.solve(root))

Input

root = TreeNode(2)
root.left = TreeNode(10)
root.right = TreeNode(4)
root.right.left = TreeNode(8)
root.right.right = TreeNode(2)
root.right.left.left = TreeNode(6)

Output

5