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Programming and Data Structures · Recursion
Official IIT answer key · IIT Roorkee · Audited Aug 2026
GATE CSE 2017 Set 1 Q35 · MCQ · 2 marks
void fun1(int n) {
if(n == 0) return;
printf("%d", n);
fun2(n - 2);
printf("%d", n);
}
void fun2(int n) {
if(n == 0) return;
printf("%d", n);
fun1(++n);
printf("%d", n);
}
The output printed when fun1(5) is called isKey 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 the following two functions. void fun1(int n) if(n == 0) return; printf("%d", n); fun2(n - 2); printf("%d", n); void fun2(int n) if(n == 0) return; printf("%d", n); fun1(++n); printf("%d", n); The output printed when fun1(5) is called is
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Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.