Function calling in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested function calls

What is the output of this C++ code when the main function runs?

C++

#include <iostream>

int add(int a, int b) {
    return a + b;
}

int multiply(int x, int y) {
    return x * y;
}

int main() {
    int result = multiply(add(2, 3), 4);
    std::cout << result << std::endl;
    return 0;
}

A 10

B 24

C 20

D 14

💡 Hint

Remember to evaluate the inner function call first before the outer one.

The add function returns 5 (2 + 3). Then multiply(5, 4) returns 20.

❓ Predict Output

intermediate

Function call with default arguments

What will be printed when this program runs?

C++

#include <iostream>
#include <string>

void greet(std::string name = "Guest") {
    std::cout << "Hello, " << name << "!" << std::endl;
}

int main() {
    greet();
    greet("Alice");
    return 0;
}

A Hello, Alice!\nHello, Guest!

B Hello, !\nHello, Alice!

C Hello, Guest!\nHello, Guest!

D Hello, Guest!\nHello, Alice!

💡 Hint

Check what happens when you call greet() without arguments.

The first call uses the default argument "Guest". The second call uses "Alice".

🔧 Debug

advanced

Identify the error in function call

What error will this code produce when compiled?

C++

#include <iostream>

void printSum(int a, int b) {
    std::cout << a + b << std::endl;
}

int main() {
    printSum(5);
    return 0;
}

A Output: 5

B Compilation error: too few arguments to function 'printSum'

C Runtime error: segmentation fault

D Output: 0

💡 Hint

Check how many arguments the function expects versus how many are given.

printSum requires two int arguments, but only one is provided, causing a compile error.

❓ Predict Output

advanced

Function call with reference parameter

What is the output of this program?

C++

#include <iostream>

void increment(int &num) {
    num += 1;
}

int main() {
    int x = 10;
    increment(x);
    std::cout << x << std::endl;
    return 0;
}

A 11

B 10

C Compilation error

D Runtime error

💡 Hint

The function changes the original variable by reference.

The increment function adds 1 to the original variable x by reference, so x becomes 11.

🧠 Conceptual

expert

Understanding function call stack behavior

Consider this code snippet. What is the value of result after main finishes?

C++

#include <iostream>

int factorial(int n) {
    if (n <= 1) return 1;
    return n * factorial(n - 1);
}

int main() {
    int result = factorial(4);
    return 0;
}

A 24

B 10

C 120

D 1

💡 Hint

Recall how factorial is calculated recursively.

factorial(4) = 4 * 3 * 2 * 1 = 24.