Return inside loops in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this C++ code with return inside a loop?

Look at the code below. What will it print when run?

C++

#include <iostream>

int findFirstEven(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        if (arr[i] % 2 == 0) {
            return arr[i];
        }
    }
    return -1;
}

int main() {
    int numbers[] = {3, 7, 5, 8, 10};
    std::cout << findFirstEven(numbers, 5);
    return 0;
}

A 8

B 3

C -1

D 10

💡 Hint

Return inside the loop stops the function immediately when condition is met.

The function checks each number in order. It returns the first even number it finds. The first even number is 8, so it prints 8.

❓ Predict Output

intermediate

What does this function return when no return is inside the loop?

What will this C++ function return when called with the array below?

C++

#include <iostream>

int findNegative(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        if (arr[i] < 0) {
            break;
        }
    }
    return 0;
}

int main() {
    int data[] = {1, 2, 3, 4, 5};
    std::cout << findNegative(data, 5);
    return 0;
}

A Undefined behavior

B 1

C Compilation error

D 0

💡 Hint

Notice the function returns 0 after the loop finishes.

The loop never finds a negative number, so it never breaks early. The function returns 0 at the end.

🔧 Debug

advanced

Why does this function always return 0?

Examine the code below. The function is supposed to return the first positive number, but it always returns 0. Why?

C++

#include <iostream>

int firstPositive(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        if (arr[i] > 0) {
            return 0;
        }
    }
    return -1;
}

int main() {
    int nums[] = {-3, -1, 4, 5};
    std::cout << firstPositive(nums, 4);
    return 0;
}

A The function returns 0 inside the loop instead of the positive number.

B The loop never runs because size is zero.

C The function has a syntax error and won't compile.

D The function returns -1 before the loop starts.

💡 Hint

Look carefully at what is returned inside the loop.

The function returns 0 inside the loop instead of the positive number found. So it never returns the actual positive number.

📝 Syntax

advanced

Which option causes a compilation error due to return inside loop?

Which of the following code snippets will cause a compilation error?

A int foo() { for(int i=0; i<3; i++) return i; }

B int foo() { for(int i=0; i<3; i++) { if(i==2) return; } return 0; }

C int foo() { for(int i=0; i<3; i++) { if(i==2) return i; } return 0; }

D int foo() { for(int i=0; i<3; i++) { if(i==2) return i; } }

💡 Hint

Check if the return statements match the function's return type.

Option B tries to return nothing (void) in a function declared to return int, causing a compilation error.

🚀 Application

expert

What is the output of this nested loop with return inside inner loop?

Consider the following C++ code. What will it print?

C++

#include <iostream>

int nestedLoop() {
    for (int i = 1; i <= 3; i++) {
        for (int j = 1; j <= 3; j++) {
            if (i * j > 3) {
                return i * j;
            }
        }
    }
    return 0;
}

int main() {
    std::cout << nestedLoop();
    return 0;
}

A 0

B 6

C 4

D 9

💡 Hint

The function returns as soon as the product i*j is greater than 3.

The first product greater than 3 is 2*2=4, so the function returns 4 immediately.