Programming and Data Structures · Trees
Official IIT answer key · IIT Bombay · Audited Aug 2026
GATE CSE 2021 Set 2 Q16 · NAT · 1 mark
Key concept
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Topic notes
In GATE CS, the 'Trees' topic tests structural counting relations in binary trees, tree traversal techniques (standard, custom, and multi-way tree traversals), tree reconstruction from sequences, expression tree evaluations, and recursive algorithms over binary/multi-way tree representations. Questions are heavily weighted towards 1-mark foundational items (both MCQ and NAT) with 2-mark questions focusing on code analysis or expression optimization.
Full Trees guide →Consider a complete binary tree with 7 nodes. Let A denote the set of first 3 elements obtained by performing Breadth-First Search (BFS) starting from the root. Let B denote the set of first 3 elements obtained by performing Depth-First Search (DFS) starting from the root. The value of |A - B| is …
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