GATE | GATE-CS-2016 (Set 2) | Question 46
Consider the following New-order strategy for traversing a binary tree:
Visit the root;
Visit the right subtree using New-order
Visit the left subtree using New-order
The New-order traversal of the expression tree corresponding to the reverse polish expression 3 4 * 5 – 2 ˆ 6 7 * 1 + – is given by:
(A) + – 1 6 7 * 2 ˆ 5 – 3 4 *
(B) – + 1 * 6 7 ˆ 2 – 5 * 3 4
(C) – + 1 * 7 6 ˆ 2 – 5 * 4 3
(D) 1 7 6 * + 2 5 4 3 * – ˆ –
Answer: (C)
Explanation:
Reverse Polish expression is derived through Post-Order i.e.
1) Â Visit Left Node
 2)  Visit Right Node                   (L R N)
 3)  Visit Root Node
— Acc. to Ques. New Order algorithm is :
  1)  Visit Root Node
  2)  Visit Right Node                   (N R L)
  3)  Visit Left Node
ie. New Order Expression will be a total reverse of the Post-Order algorithm
Post-Order Expression        :  3 4 * 5 – 2 ˆ 6 7 * 1 + –
Hence , New Order Expression :  – + 1 * 7 6 ^ 2 – 5 * 4 3Â
This solution is contributed by Mohit Gupta.
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Last Updated :
28 Jun, 2021
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