Programming and Data Structures · Recursion
Official IIT answer key · IIT Kharagpur · Audited Aug 2026
GATE CSE 2014 Set 1 Q12 · NAT · 1 mark
Key concept
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Topic notes
GATE tests Recursion primarily through direct execution tracing of recursive C code snippets, stack-unwinding behavior (pre-order vs. post-order execution), and termination/infinite recursion analysis. Questions frequently incorporate static variables, pointer/reference aliasing, mutual recursion, and tree/array traversals to test whether candidates can systematically maintain call frames. In recent years, the focus has expanded from standard tracing to higher-order mathematical characterizations (e.g., finding the smallest input or maximum output value of composed recurrences).
Full Recursion guide →Consider a rooted n node binary tree represented using pointers. The best upper bound on the time required to determine the number of subtrees having exactly 4 nodes is O(na b n). Then the value of a + 10b is …
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