Return values in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this C function call?

Consider the following C code snippet. What will be printed when printf("%d", add(3, 4)); is executed?

C

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

int main() {
    printf("%d", add(3, 4));
    return 0;
}

A Compilation error

B 34

C 0

D 7

💡 Hint

Remember that the return statement sends back the sum of the two numbers.

The function add returns the sum of a and b. So, add(3, 4) returns 7, which is printed.

❓ Predict Output

intermediate

What value does this function return?

What is the return value of the function mystery when called with mystery(5)?

C

int mystery(int x) {
    if (x > 0) {
        return x * 2;
    } else {
        return -1;
    }
}

A 10

B -1

C 0

D Undefined behavior

💡 Hint

Check the condition and what happens when x is positive.

Since 5 is greater than 0, the function returns 5 * 2 = 10.

❓ Predict Output

advanced

What is the output of this recursive function?

What will be printed when printf("%d", factorial(4)); is executed?

C

int factorial(int n) {
    if (n == 0) {
        return 1;
    } else {
        return n * factorial(n - 1);
    }
}

int main() {
    printf("%d", factorial(4));
    return 0;
}

A 24

B 10

C 0

D Stack overflow error

💡 Hint

Recall that factorial of 4 is 4 * 3 * 2 * 1.

The function calculates factorial recursively. factorial(4) = 4 * factorial(3) = 24.

❓ Predict Output

advanced

What error does this function cause?

What happens when int result = no_return(); is executed given the function below?

C

int no_return() {
    int x = 5;
    x += 3;
    // Missing return statement
}

int main() {
    int result = no_return();
    printf("%d", result);
    return 0;
}

A Prints 8

B Compilation warning or undefined behavior

C Prints 0

D Runtime error: segmentation fault

💡 Hint

Functions declared to return a value must have a return statement.

The function no_return lacks a return statement, which leads to undefined behavior or compiler warnings.

🧠 Conceptual

expert

What is the value of x after this function call?

Given the code below, what is the value of x after x = update(10); is executed?

C

int update(int a) {
    a = a + 5;
    return a;
}

int main() {
    int x = 0;
    x = update(10);
    return 0;
}

A 0

B 10

C 15

D Compilation error

💡 Hint

The function returns the updated value of a.

The function adds 5 to the input and returns it. So x becomes 15.