C#: Create a new string of the characters at indexes 0,1, 4,5, 8,9 ... from a given string

Last update on June 25 2025 13:02:56 (UTC/GMT +8 hours)

Characters at Index 0,1,4,5,...

Write a C# Sharp program to create a string of characters at indexes 0,1, 4,5, 8,9 ... from a given string.

Visual Presentation:

Sample Solution:-

C# Sharp Code:

using System;
using System.Linq;

namespace exercises
{
    // Class declaration
    class Program
    {
        // Main method - entry point of the program
        static void Main(string[] args)
        {
            // Calling the 'test' method with different strings
            Console.WriteLine(test("Python"));      // Output: Py
            Console.WriteLine(test("JavaScript"));  // Output: Ja
            Console.WriteLine(test("HTML"));        // Output: HT
            Console.ReadLine(); // Keeping the console window open
        }

        // Method to process a string and extract substrings at specific intervals
        public static string test(string str1)
        {
            var result = string.Empty; // Initializing an empty string to store the result
            for (var i = 0; i < str1.Length; i += 4) // Loop through the characters of the string with a step of 4
            {
                var c = i + 2; // Calculate the index position to start the substring
                var n = 0; // Initialize a variable to hold the length of the substring
                n += c > str1.Length ? 1 : 2; // Determine the length based on the position and length of the string
                result += str1.Substring(i, n); // Extract a substring and append it to the result
            }
            return result; // Return the final result after processing the string
        }
    }
}

Sample Output:

Pyon
JaScpt
HT

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C# program to build a string using characters at positions 0,2,4,6,8,... from a given string.
• Write a C# program to create a new string using every 4th character group of 2 characters (e.g., 0,1 then 4,5 etc.).
• Write a C# program to generate a string from indexes 0,3,6,... and 1,4,7,... interleaved together.
• Write a C# program to extract characters from every third block of 3 characters starting from the beginning of a string.

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