# Postorder Traversal Multiple choice Questions and Answers (MCQs)

## Postorder Traversal Multiple choice Questions and Answers (MCQs)

 Question 1
In postorder traversal of binary tree right subtree is traversed before visiting root.
 A True B False
Question 1 Explanation:
Post-order method of traversing involves - i) Traverse left subtree in post-order, ii) Traverse right subtree in post-order, iii) visit the root.

 Question 2
What is the possible number of binary trees that can be created with 3 nodes, giving the sequence N, M, L when traversed in post-order.
 A 15 B 3 C 5 D 8
Question 2 Explanation:
5 binary trees are possible and they are,

 Question 3
The post-order traversal of a binary tree is O P Q R S T. Then possible pre-order traversal will be .....
 A T Q R S O P B T O Q R P S C T Q O P S R D T Q O S P R
Question 3 Explanation:
The last, second last nodes visited in post-order traversal are root and it's right child respectively. Option T Q R S O P can't be a pre-order traversal, because nodes O, P are visited after the nodes Q, R, S. Option T O Q R P S, can't be valid, because the pre-order sequence given in option T O Q R P S and given post-order traversal creates a tree with node T as root and node O as left subtree. Option T Q O P S R is valid. Option T Q O S P R is not valid as node P is visited after visiting node S.

 Question 4
A binary search tree contains values 7, 8, 13, 26, 35, 40, 70, 75. Which one of the following is a valid post-order sequence of the tree provided the pre-order sequence as 35, 13, 7, 8, 26, 70, 40 and 75?
 A 7, 8, 26, 13, 75, 40, 70, 35 B 26, 13, 7, 8, 70, 75, 40, 35 C 7, 8, 13, 26, 35, 40, 70, 75 D 8, 7, 26, 13, 40, 75, 70, 35
Question 4 Explanation:
The binary tree contains values 7, 8, 13, 26, 35, 40, 70, 75. The given pre-order sequence is 35, 13, 7, 8, 26, 70, 40 and 75. So, the binary search tree formed is

Thus post-order sequence for the tree is 8, 7, 26, 13, 40, 75, 70 and 35.

 Question 5
Which of the following pair's traversals on a binary tree can build the tree uniquely?
 A post-order and pre-order B post-order and in-order C post-order and level order D level order and preorder