Multiple input and output in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with multiple inputs and outputs using references

What is the output of the following C++ program?

C++

#include <iostream>
using namespace std;

void updateValues(int a, int& b, int& c) {
    a = a + 10;
    b = b + 20;
    c = c + 30;
}

int main() {
    int x = 1, y = 2, z = 3;
    updateValues(x, y, z);
    cout << x << " " << y << " " << z << endl;
    return 0;
}

A 1 22 33

B 11 22 33

C 11 2 3

D 1 2 3

💡 Hint

Remember that only variables passed by reference can be changed outside the function.

The variable 'a' is passed by value, so changes inside the function do not affect 'x'. Variables 'b' and 'c' are passed by reference, so their values are updated.

❓ Predict Output

intermediate

Output of function returning multiple values via pointers

What will be printed by this C++ program?

C++

#include <iostream>
using namespace std;

void compute(int a, int b, int* sum, int* product) {
    *sum = a + b;
    *product = a * b;
}

int main() {
    int x = 4, y = 5, s = 0, p = 0;
    compute(x, y, &s, &p);
    cout << s << " " << p << endl;
    return 0;
}

A 45 9

B 9 9

C 9 20

D 20 9

💡 Hint

Pointers allow the function to modify variables outside its scope.

The function sets '*sum' to 4+5=9 and '*product' to 4*5=20, so the output is '9 20'.

🔧 Debug

advanced

Identify the error in multiple output function using references

This code is intended to swap two integers using references. What is the output of this C++ program?

C++

#include <iostream>
using namespace std;

void swap(int a, int b) {
    int temp = a;
    a = b;
    b = temp;
}

int main() {
    int x = 10, y = 20;
    swap(x, y);
    cout << x << " " << y << endl;
    return 0;
}

A Compilation error: missing & in function parameters

B Output: 10 20

C Output: 20 10

D Runtime error: segmentation fault

💡 Hint

Check how the function parameters are passed and if changes affect the original variables.

The function parameters are passed by value, so swapping inside the function does not affect 'x' and 'y'. The output remains '10 20'.

❓ Predict Output

advanced

Output of function returning multiple values using std::tuple

What is the output of this C++ program that returns multiple values using std::tuple?

C++

#include <iostream>
#include <tuple>
using namespace std;

tuple<int, int> minMax(int a, int b) {
    if (a < b) return {a, b};
    else return {b, a};
}

int main() {
    int x = 7, y = 3;
    auto [minVal, maxVal] = minMax(x, y);
    cout << minVal << " " << maxVal << endl;
    return 0;
}

A 3 7

B 7 3

C 0 0

D Compilation error: structured bindings not supported

💡 Hint

Structured bindings unpack the tuple into variables.

The function returns the smaller and larger values correctly. Structured bindings assign them to minVal and maxVal.

🧠 Conceptual

expert

Understanding multiple output methods in C++ functions

Which of the following statements about returning multiple outputs from a C++ function is NOT true?

A Functions can only return one value directly, so multiple outputs need workarounds.

B Returning a std::tuple can return multiple values but requires unpacking by the caller.

C Using references as function parameters allows modifying variables outside the function.

D Using pointers as parameters is unsafe and always causes runtime errors.

💡 Hint

Think about pointer usage and safety in C++.

Pointers can be used safely if handled correctly. They do not always cause runtime errors.