Refactoring Loops

Part of the Logic & Flow section of Coddy's C# journey — lesson 16 of 66.

Refactoring loops can improve code readability and maintainability.

Replace traditional loop with foreach for simplicity:

string[] fruits = { "apple", "banana", "cherry" };

// Before refactoring
for (int i = 0; i < fruits.Length; i++)
{
    Console.WriteLine(fruits[i]);
}

// After refactoring
foreach (string fruit in fruits)
{
    Console.WriteLine(fruit);
}

Extract complex loop logic into methods:

int[] numbers = { 1, 2, 3, 4, 5, 6 };

// Before refactoring
for (int i = 0; i < numbers.Length; i++)
{
    if (numbers[i] % 2 == 0)
    {
        Console.WriteLine($"{numbers[i]} is even");
    }
}

// After refactoring with helper method
for (int i = 0; i < numbers.Length; i++)
{
    if (IsEven(numbers[i]))
    {
        Console.WriteLine($"{numbers[i]} is even");
    }
}

// Helper method
bool IsEven(int number)
{
    return number % 2 == 0;
}

Break large loops into smaller, more focused loops:

int[] data = { 1, 2, 3, 4, 5 };

// Before: One large loop doing multiple things
for (int i = 0; i < data.Length; i++)
{
    // Process data
    data[i] = data[i] * 2;
    // Print results
    Console.WriteLine(data[i]);
}

// After: Separate loops with clear purposes
// Process data
for (int i = 0; i < data.Length; i++)
{
    data[i] = data[i] * 2;
}

// Print results
for (int i = 0; i < data.Length; i++)
{
    Console.WriteLine(data[i]);
}

Challenge

Medium

Create a method called refactorArrayFilter that:

Takes an array of integers as a parameter
Implements two versions of code that count numbers divisible by 3:
- Original: Use a traditional for loop with an if statement
- Refactored: Use a foreach loop with the logic extracted to a helper method
Returns the count from the refactored version as an integer

For example, given the array [3, 4, 6, 7, 9], the method should return 3 because there are three numbers (3, 6, and 9) that are divisible by 3.

Note: You don't need to print anything - just return the count as an integer.

Cheat sheet

Use foreach instead of traditional for loops for simpler array iteration:

// Traditional for loop
for (int i = 0; i < fruits.Length; i++)
{
    Console.WriteLine(fruits[i]);
}

// Refactored with foreach
foreach (string fruit in fruits)
{
    Console.WriteLine(fruit);
}

Extract complex loop logic into helper methods:

// Before refactoring
if (numbers[i] % 2 == 0)
{
    Console.WriteLine($"{numbers[i]} is even");
}

// After refactoring with helper method
if (IsEven(numbers[i]))
{
    Console.WriteLine($"{numbers[i]} is even");
}

// Helper method
bool IsEven(int number)
{
    return number % 2 == 0;
}

Break large loops into smaller, focused loops with single responsibilities:

// Before: One loop doing multiple things
for (int i = 0; i < data.Length; i++)
{
    data[i] = data[i] * 2;  // Process
    Console.WriteLine(data[i]);  // Print
}

// After: Separate loops with clear purposes
for (int i = 0; i < data.Length; i++)
{
    data[i] = data[i] * 2;  // Process only
}

for (int i = 0; i < data.Length; i++)
{
    Console.WriteLine(data[i]);  // Print only
}

Try it yourself

public class RefactorArrayFilter
{
    // Implement the refactorArrayFilter method
    public static int refactorArrayFilter(int[] numbers)
    {
        // Write your code here
        
    }
    
    // Implement any helper methods you need
}