Call stack behavior in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to call the function foo.

C++

#include <iostream>

void foo() {
    std::cout << "Hello from foo!" << std::endl;
}

int main() {
    [1];
    return 0;
}

Drag options to blanks, or click blank then click option'

Afoo()

Bfoo

Ccall foo()

Dfoo();

Attempts:

3 left

💡 Hint

Common Mistakes

Writing only the function name without parentheses.

Adding extra words like 'call' before the function name.

To call a function in C++, you write its name followed by parentheses. So foo() calls the function.

2fill in blank

medium

Complete the code to make bar call foo.

C++

#include <iostream>

void foo() {
    std::cout << "Inside foo" << std::endl;
}

void bar() {
    [1];
}

int main() {
    bar();
    return 0;
}

Drag options to blanks, or click blank then click option'

Afoo();

Bfoo

Ccall foo()

Dfoo()

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting parentheses when calling the function.

Adding extra words like 'call' before the function name.

Inside a function, to call another function, use its name with parentheses like foo().

3fill in blank

hard

Fix the error in the recursive function countdown to avoid infinite recursion.

C++

#include <iostream>

void countdown(int n) {
    if (n == 0) {
        std::cout << "Done!" << std::endl;
        return;
    }
    std::cout << n << std::endl;
    countdown([1]);
}

int main() {
    countdown(3);
    return 0;
}

Drag options to blanks, or click blank then click option'

A0

Bn + 1

Cn - 1

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Calling with the same number causing infinite recursion.

Increasing the number instead of decreasing.

To count down, you need to call countdown with n - 1 so the number decreases each time.

4fill in blank

hard

Fill both blanks to create a dictionary-like map of numbers to their squares using a loop.

C++

#include <iostream>
#include <map>

int main() {
    std::map<int, int> squares;
    for (int [1] = 1; [2] <= 5; ++i) {
        squares[i] = i * i;
    }
    for (const auto& [key, value] : squares) {
        std::cout << key << ": " << value << std::endl;
    }
    return 0;
}

Drag options to blanks, or click blank then click option'

Ai

Bj

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in initialization and condition.

Using variables not declared in the loop.

The loop variable should be the same in initialization and condition. Here, i is used.

5fill in blank

hard

Fill all three blanks to create a recursive function that sums numbers from n down to 1.

C++

#include <iostream>

int sum_to_n(int [1]) {
    if ([2] == 0) {
        return 0;
    }
    return [3] + sum_to_n([2] - 1);
}

int main() {
    std::cout << sum_to_n(5) << std::endl;
    return 0;
}

Drag options to blanks, or click blank then click option'

An

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing errors.

Forgetting to decrease the number in the recursive call.

The function parameter and recursive calls use the same variable n to sum down to zero.