GATE 2013 CS (CS1) – Question 53

Programming and Data Structures · Trees and Binary Search Trees · 2 marks · Multiple choice

A BST has preorder 30,20,10,15,25,23,39,35,42. Find its postorder.

10,20,15,23,25,35,42,39,30
15,10,25,23,20,42,35,39,30
15,20,10,23,25,42,35,39,30
15,10,23,25,20,35,42,39,30

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Show answer and explanation

Correct answer: (D) 15,10,23,25,20,35,42,39,30

Explanation

Root thirty separates left subtree 20,10,15,25,23 and right subtree 39,35,42. Left postorder is 15,10,23,25,20; right postorder is 35,42,39. Append root thirty to obtain D. Each recursive split follows the BST ordering property.

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