Basic C# Coding Questions For Technical Interviews

Introduction

Here, we will try a few frequently asked .NET C# programming questions in technical interviews.

We will be coding everything from scratch and not using any built-in library/functions like “substring”, “LINQ” because in the easy questions the other side wants us to show that we know basics.

In case where a bigger logical problem statement is given we generally use in built libs and functions.

1- Reverse a string in C#?

Now as an answer this can have many variations like:

• Don’t use an extra variable
• Or try to use string builder or char array etc

Use your PC or online

C# Online Compiler | .NET Fiddle

First solution using an extra variable and for loop.

using System;
     
public class Program
{
   public static void Main()
   {  
      String str = "ABCD EFGH Z";
      Console.WriteLine(str);
    
      string strReversed = "";
      //start reading character from end of the string
      for(int i = str.Length - 1; i >= 0; i--){
        strReversed += str[i];
      }
      Console.WriteLine(strReversed);  
   }
}

https://dotnetfiddle.net/Widget/7BT1Ur

Another solution using extra character array, two pointers, swap, and loop.

using System;
     
public class Program
{
   public static void Main()
   {  
      String str = "AAA Z";
      Console.WriteLine(str);
      
      char[] charArray = str.ToCharArray();
      //Start reading th string from both ends (start and end)
      //this loop runs length/2 times 
      for (int i = 0, j = str.Length - 1; i < j; i++, j--)  
      {  
         charArray[i] = str[j];//read from start of the string & add into char array
         charArray[j] = str[i];//read from end of the string & add into char array
      }  
      string strReversed = new string(charArray);  
      Console.WriteLine(strReversed);  
   }
}

https://dotnetfiddle.net/UqKxDZ

There are more ways to do it, we shall explore them in coming time.

Till then Mirror — Mirror — Code Mirror.