Flatten Nested Conditionals

Part of the Logic & Flow section of Coddy's C# journey — lesson 22 of 66.

Nested conditionals can make your code hard to read and maintain. Flattening helps improve readability by reducing indentation levels.

Here's an example of deeply nested conditionals:

if (userLoggedIn)
{
    if (userHasPermission)
    {
        if (fileExists)
        {
            // Process the file
            ProcessFile();
        }
        else
        {
            Console.WriteLine("File not found");
        }
    }
    else
    {
        Console.WriteLine("No permission");
    }
}
else
{
    Console.WriteLine("Not logged in");
}

We can flatten this using early returns or guard clauses:

if (!userLoggedIn)
{
    Console.WriteLine("Not logged in");
    return;
}

if (!userHasPermission)
{
    Console.WriteLine("No permission");
    return;
}

if (!fileExists)
{
    Console.WriteLine("File not found");
    return;
}

// Process the file
ProcessFile();

Notice how the flattened code has less indentation and is easier to follow.

Challenge

Easy

In scholarship eligibility checking, deeply nested conditionals make the code hard to read and maintain. In this challenge, you'll transform a messy nested conditional structure into clean, readable code using guard clauses.

A guard clause is an early return statement that handles a specific condition right away, allowing the rest of the function to focus on the "happy path".

Your task is to complete the partially implemented guard clauses in the CheckScholarshipEligibility method according to these rules:

If age is less than 17, return "Not eligible due to age requirement" immediately
If GPA ≥ 3.5 AND the student has a recommendation, grant full scholarship
If GPA ≥ 3.8, grant full scholarship (even without recommendation)
If GPA ≥ 3.0 AND the student has a recommendation, grant partial scholarship
If GPA is between 3.5 and 3.8, grant partial scholarship
For all other cases, return "Not eligible for scholarship"

Cheat sheet

Nested conditionals can make code hard to read and maintain. Flattening helps improve readability by reducing indentation levels.

Instead of deeply nested conditionals:

if (userLoggedIn)
{
    if (userHasPermission)
    {
        if (fileExists)
        {
            // Process the file
            ProcessFile();
        }
        else
        {
            Console.WriteLine("File not found");
        }
    }
    else
    {
        Console.WriteLine("No permission");
    }
}
else
{
    Console.WriteLine("Not logged in");
}

Use early returns or guard clauses to flatten the structure:

if (!userLoggedIn)
{
    Console.WriteLine("Not logged in");
    return;
}

if (!userHasPermission)
{
    Console.WriteLine("No permission");
    return;
}

if (!fileExists)
{
    Console.WriteLine("File not found");
    return;
}

// Process the file
ProcessFile();

A guard clause is an early return statement that handles a specific condition right away, allowing the rest of the function to focus on the "happy path".

Try it yourself

using System;

class Program
{
    public static void CheckScholarshipEligibility(int age, double gpa, bool hasRecommendation)
    {
        // Guard clause for age requirement
        if (age < 17)
        {
            Console.WriteLine("Not eligible due to age requirement.");
            return;
        }
        
        // Guard clause for full scholarship with recommendation
        if (/* Complete this condition */)
        {
            Console.WriteLine("Full scholarship granted!");
            return;
        }
        
        // Guard clause for full scholarship with exceptional GPA
        if (/* Complete this condition */)
        {
            Console.WriteLine("Full scholarship granted!");
            return;
        }
        
        // Guard clause for partial scholarship with recommendation
        if (/* Complete this condition */)
        {
            Console.WriteLine("Partial scholarship granted.");
            return;
        }
        
        // Guard clause for partial scholarship with good GPA
        if (/* Complete this condition */)
        {
            Console.WriteLine("Partial scholarship granted.");
            return;
        }
        
        // Default case: not eligible
        Console.WriteLine("Not eligible for scholarship.");
    }
    
    static void Main(string[] args)
    {
        // Test cases for immediate feedback
        Console.WriteLine("Test Case 1: Age 16, GPA 4.0, Has Recommendation: True");
        CheckScholarshipEligibility(16, 4.0, true);
        
        Console.WriteLine("\nTest Case 2: Age 18, GPA 3.9, Has Recommendation: False");
        CheckScholarshipEligibility(18, 3.9, false);
        
        Console.WriteLine("\nTest Case 3: Age 17, GPA 3.6, Has Recommendation: True");
        CheckScholarshipEligibility(17, 3.6, true);
        
        Console.WriteLine("\nTest Case 4: Age 19, GPA 3.2, Has Recommendation: True");
        CheckScholarshipEligibility(19, 3.2, true);
        
        Console.WriteLine("\nTest Case 5: Age 18, GPA 2.8, Has Recommendation: False");
        CheckScholarshipEligibility(18, 2.8, false);
    }
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Logic & Flow

1Multi-dimensional Arrays

2D Arrays Basics Declaring and Initializing 2D Accessing 2D Array Elements Nested Loops with 2D Arrays Jagged Arrays Common Matrix Operations Recap - Multi-dimensional

4Flow Control Techniques

Early Returns Guard Clauses Jump Statements (goto)Break and ContinueFlatten Nested Conditionals

7Logical Operators Advanced

Short-Circuit Evaluation Conditional Logical Operators Operator Precedence Recap - Advanced Operators

10HashMap Part 2

HashMap Methods Nested HashMap Recap - Manage Warehouse Recap - HashMap Operations