Consider the following C program:
#include <stdio.h>
int g(int n) {
return (n+10);
}
int f(int n) {
return g(n*2);
}
int main() {
int sum, n;
sum=0;
for (n=1; n<3; n++)
sum += g(f(n));
printf ("%d", sum);
return 0;
}The output of the given C program is ________. (Answer in integer)
ANSWER
The output of the program is 46.
Official answer: 46Source: Official answer key, GATE 2025 CS2 (IIT Roorkee)
g(n) returns n+10, so f(n) = g(n*2) = 2n+10.
The for-loop runs for n=1 and n=2 (loop stops when n<3 fails, i.e. at n=3).
n=1: f(1) = 2(1)+10 = 12. g(f(1)) = g(12) = 12+10 = 22. sum = 0+22 = 22.
n=2: f(2) = 2(2)+10 = 14. g(f(2)) = g(14) = 14+10 = 24. sum = 22+24 = 46.
The loop ends; printf outputs the value of sum, which is 46.
KEY IDEA
Trace nested function calls exactly in evaluation order: g(f(n)) first fully evaluates f(n), which itself calls g(n*2), before the outer g is applied to that result.
WATCH OUT FOR
Applying g only once per loop iteration (forgetting that f(n) internally already calls g), e.g. computing sum += n*2+10 instead of sum += g(f(n)) = (n*2+10)+10, which gives 36 instead of 46.
From the GATE 2025 CS2 paper. Every question of this paper · Download the full paper · All 7 Functions & scope questions, with notes
