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

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of overloaded functions with different parameter types

What is the output of this C++ program?

C++

#include <iostream>
using namespace std;

void print(int x) {
    cout << "Int: " << x << endl;
}

void print(double x) {
    cout << "Double: " << x << endl;
}

int main() {
    print(5);
    print(5.5);
    return 0;
}

A

Double: 5
Double: 5.5

B

Int: 5
Double: 5.5

C

Int: 5
Int: 5

D Compilation error due to ambiguous call

💡 Hint

Look at the parameter types of each overloaded function and which one matches the argument.

The function print(int) is called with 5 (an int), so it prints "Int: 5". The function print(double) is called with 5.5 (a double), so it prints "Double: 5.5".

❓ Predict Output

intermediate

Which overloaded function is called with const reference?

What is the output of this C++ program?

C++

#include <iostream>
using namespace std;

void show(int &x) {
    cout << "Non-const ref: " << x << endl;
}

void show(const int &x) {
    cout << "Const ref: " << x << endl;
}

int main() {
    int a = 10;
    const int b = 20;
    show(a);
    show(b);
    return 0;
}

A

Non-const ref: 10
Const ref: 20

B

Non-const ref: 10
Non-const ref: 20

C

Const ref: 10
Const ref: 20

D Compilation error due to ambiguous call

💡 Hint

Non-const references cannot bind to const variables.

The first call show(a) uses the non-const reference version because a is non-const. The second call show(b) uses the const reference version because b is const.

❓ Predict Output

advanced

Output of overloaded functions with default parameters

What is the output of this C++ program?

C++

#include <iostream>
using namespace std;

void display(int x, int y = 5) {
    cout << "display(int, int): " << x << ", " << y << endl;
}

void display(int x) {
    cout << "display(int): " << x << endl;
}

int main() {
    display(3);
    display(3, 7);
    return 0;
}

A

display(int, int): 3, 5
display(int, int): 3, 7

B

display(int): 3
display(int): 3

C

display(int): 3
display(int, int): 3, 7

D Compilation error due to ambiguous call

💡 Hint

Default parameters do not participate in overload resolution if a better match exists.

The call display(3) matches display(int) exactly, so that is called. The call display(3,7) matches display(int,int) with both parameters, so that is called.

❓ Predict Output

advanced

Which overloaded function is called with pointer and nullptr?

What is the output of this C++ program?

C++

#include <iostream>
using namespace std;

void process(int *p) {
    cout << "Pointer version" << endl;
}

void process(bool b) {
    cout << "Bool version" << endl;
}

int main() {
    process(nullptr);
    return 0;
}

A

Pointer version

B

Bool version

C

Compilation error due to ambiguous call

D

Runtime error

💡 Hint

nullptr is a null pointer literal and prefers pointer overloads over bool.

nullptr matches the pointer version exactly. The bool version would require conversion. So the pointer version is called.

🧠 Conceptual

expert

Why does this overloaded function call cause ambiguity?

Consider these overloaded functions:

void func(int x, double y);
void func(double x, int y);

What happens when you call func(5, 5); and why?

A Calls func(int, int) which does not exist, so runtime error.

B Calls func(int, double) because int matches first parameter exactly.

C Calls func(double, int) because int converts to double better than double to int.

D Compilation error due to ambiguous call because both overloads are equally good matches.

💡 Hint

Both functions require one conversion from int to double, so compiler cannot decide.

When calling func(5,5), the first overload needs to convert second argument from int to double, the second overload needs to convert first argument from int to double. Both conversions are equally good, so the call is ambiguous and causes a compilation error.