Return inside loops in C++ - Mini Project: Build & Apply

Return inside loops

📖 Scenario: Imagine you are checking a list of numbers to find the first even number. Once you find it, you want to stop checking and return that number immediately.

🎯 Goal: You will write a function that goes through a list of numbers and returns the first even number it finds using a return statement inside a loop.

📋 What You'll Learn

Create a vector called numbers with the exact values: 3, 7, 10, 5, 8

Create an integer variable called firstEven and initialize it to -1

Write a for loop using int i = 0; i < numbers.size(); i++ to check each number

Inside the loop, use an if statement to check if the current number is even

If the number is even, use return to immediately return that number

Outside the loop, return firstEven if no even number is found

Print the returned value from the function

💡 Why This Matters

🌍 Real World

Finding the first item that meets a condition quickly is common in searching tasks, like finding the first available seat or the first error in a log.

💼 Career

Understanding how to return early from loops helps write efficient code in many programming jobs, especially when processing data or searching.

1

Create the data vector

Create a std::vector<int> called numbers with these exact values: 3, 7, 10, 5, 8

C++

#include 
#include 

int findFirstEven(const std::vector& numbers) {
    // Your code here
}

int main() {
    // Create the vector numbers here
    // Your code here
    return 0;
}

Need a hint?

Use std::vector<int> numbers = {3, 7, 10, 5, 8}; to create the vector.

2

Add a variable to hold the default return value

Inside the function findFirstEven, create an integer variable called firstEven and set it to -1

C++

#include 
#include 

int findFirstEven(const std::vector& numbers) {
    // Create firstEven variable here
    // Your code here
}

int main() {
    std::vector numbers = {3, 7, 10, 5, 8};
    return 0;
}

Need a hint?

Write int firstEven = -1; inside the function.

3

Write the loop and return inside it

Inside the function findFirstEven, write a for loop using int i = 0; i < numbers.size(); i++. Inside the loop, use an if statement to check if numbers[i] % 2 == 0. If true, immediately return numbers[i]. After the loop, return firstEven.

C++

#include 
#include 

int findFirstEven(const std::vector& numbers) {
    int firstEven = -1;
    // Add for loop and return inside it here
    // Your code here
}

int main() {
    std::vector numbers = {3, 7, 10, 5, 8};
    return 0;
}

Need a hint?

Use a for loop and inside it an if to check even numbers. Use return inside the if.

4

Call the function and print the result

In main(), call findFirstEven(numbers) and store the result in an integer variable called result. Then print result using std::cout.

C++

#include 
#include 

int findFirstEven(const std::vector& numbers) {
    int firstEven = -1;
    for (int i = 0; i  numbers = {3, 7, 10, 5, 8};
    // Call findFirstEven and print the result here
    // Your code here
    return 0;
}

Need a hint?

Call the function, save the return value in result, then print it with std::cout << result << std::endl;.