Program to find leaf and non-leaf nodes of a binary tree in Python

Suppose we have a binary tree, we have to find a list of two numbers where the first number is the count of leaves in the tree and the second number is the count of non-leaf nodes.

So, if the input is like

then the output will be (3, 2), as there are 3 leaves and 2 non-leaf nodes.

To solve this, we will follow these steps −

• if n is null, then
  • return (0, 0)
• if left of n is null and right of n is null, then
  • return (1, 0)
• left := solve(left of n)
• right := solve(right of n)
• return (left[0] + right[0], 1 + left[1] + right[1])

Let us see the following implementation to get better understanding −

Example

class TreeNode:
   def __init__(self, data, left = None, right = None):
      self.val = data
      self.left = left
      self.right = right
class Solution:
   def solve(self, n):
      if not n:
         return 0, 0
      if not n.left and not n.right:
         return 1, 0
      left, right = self.solve(n.left), self.solve(n.right)
      return left[0] + right[0], 1 + left[1] + right[1]
ob = Solution()
root = TreeNode(6)
root.left = TreeNode(2)
root.right = TreeNode(6)
root.right.left = TreeNode(10)
root.right.right = TreeNode(2)
print(ob.solve(root))

Input

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

Output

(3, 2)