🔢 Day 1: Mastering Data Types and Input/Output in C# – A HackerRank Practice Challenge

If you're just getting started with C#, this HackerRank challenge is an ideal warm-up. It introduces key concepts like data types, console input/output, and string operations — all foundational for any aspiring C# developer.

Let’s break down the challenge and explore why it matters — with improved depth, real-world considerations, and a quick exercise at the end.

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📌 Objective

You're given three predefined variables:

int i = 4;

double d = 4.0;

string s = "HackerRank ";

Your task is to:

1. Declare three new variables: one int, one double, and one string.

2. Read user input for each variable.

3. Perform the following operations:

   • Add your int to i

   • Add your double to d (print with 1 decimal place)

   • Concatenate your string with s and print the result

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📥 Sample Input

12

4.0

is the best place to learn and practice coding!

📤 Sample Output

16

8.0

HackerRank is the best place to learn and practice coding!

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🧪 Step-by-Step Solution in C#

Here’s the full, working solution with inline comments and clarity:

using System;

class Solution {

static void Main(String[] args) {

// Predefined variables

int i = 4;

double d = 4.0;

string s = "HackerRank ";

// Declare second integer, double, and string variables

int i2;

double d2;

string s2;

// Read and convert inputs from string to appropriate types

i2 = Convert.ToInt32(Console.ReadLine()); // Converts string to int

d2 = Convert.ToDouble(Console.ReadLine()); // Converts string to double

s2 = Console.ReadLine(); // Reads string as-is

// Print the sum of integers

Console.WriteLine(i + i2);

// Print the sum of doubles, formatted to 1 decimal place

Console.WriteLine((d + d2).ToString("F1"));

// Concatenate and print strings

Console.WriteLine(s + s2);

}

}

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❓ Why Type Conversion Is Necessary

All input from Console.ReadLine() is read as a string, even if the user types a number. So, to perform math, you must explicitly convert it.

// User enters: "12"

int num = Convert.ToInt32("12"); // Now it's usable in math

🛑 Note: If a user enters invalid data (e.g., "abc"), Convert.ToInt32() or Convert.ToDouble() will throw a runtime exception.

🔒 You can catch these using a try-catch block (more on that in the mini challenge!).

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🔍 Key Learnings

✅ Declare and use different data types in C#
✅ Read input from the console using Console.ReadLine()
✅ Convert strings to numbers with Convert.ToInt32() and Convert.ToDouble()
✅ Format floating-point output using .ToString("F1")
✅ Concatenate strings using the + operator

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💡 Bonus Tip

In coding platforms like HackerRank, always format double values to match the exact output format.

double result = 4.0 + 4.0;

Console.WriteLine(result.ToString("F1")); // Output: 8.0

This prevents test case mismatches like printing 8 instead of 8.0.

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🧠 Mini Challenge for You

Try this quick variation on your own:

You're given:

int i = 7;

double d = 3.14;

string s = "Learning ";

🎯 Task:

• Read input values from the user.

• Add and concatenate as before.

• Print the results using the same format.

• ✨ Bonus: Try wrapping your input in try-catch to handle invalid input gracefully.

Share your code or output in the comments below!

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👨‍💻 Final Thoughts

This challenge might look basic, but it’s crucial. Reading input, converting types, and formatting output are skills you’ll use in nearly every program.

💪 Small, consistent practice like this builds the confidence needed to tackle bigger real-world projects.

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✅ Did this help?

If so, leave a ❤️ or share your variation in the comments!
Let’s keep leveling up together — one problem at a time.