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Programming and Data Structures · Recursion
Official IIT answer key · IIT Bombay · Audited Aug 2026
GATE CSE 2021 Set 2 Q49 · NAT · 2 marks
#include <stdio.h>
int foo(int x, int y, int q)
{
if ((x <= 0) && (y <= 0))
return q;
if (x <= 0)
return foo(x, y-q, q);
if (y <= 0)
return foo(x-q, y, q);
return foo(x, y-q, q) + foo(x-q, y, q);
}
int main()
{
int r = foo(15,15,10);
printf("%d", r);
return 0;
}
The output of the program upon execution is ________.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 the following ANSI C program. #include int foo(int x, int y, int q) if ((x The output of the program upon execution is …
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