C#: Compare two given strings and return the number of the positions where they contain the same substring of length 2

Last update on June 25 2025 13:03:52 (UTC/GMT +8 hours)

Count Matching Substrings in Two Strings

Write a C# Sharp program to compare two given strings and return the number of positions where they contain the same length of 2 substrings.

Sample Solution:-

C# Sharp Code:

using System;
using System.Linq;

// Namespace declaration
namespace exercises
{
    // Class declaration
    class Program
    {
        // Main method - entry point of the program
        static void Main(string[] args)
        {
            // Calling the 'test' method with different pairs of strings
            Console.WriteLine(test("abcdefgh", "abijsklm")); // Output: 3
            Console.WriteLine(test("abcde", "osuefrcd"));   // Output: 1
            Console.WriteLine(test("pqrstuvwx", "pqkdiewx"));// Output: 2
            Console.ReadLine(); // Keeping the console window open
        }

        // Method to count occurrences of two-character substrings that are common in both input strings
        public static int test(string str1, string str2)
        {
            var ctr = 0; // Counter to track the occurrences of common two-character substrings

            // Iterate through the first string's characters except the last one
            for (var i = 0; i < str1.Length - 1; i++)
            {
                var firstString = str1.Substring(i, 2); // Extract a two-character substring from the first string

                // Iterate through the second string's characters except the last one
                for (var j = 0; j < str2.Length - 1; j++)
                {
                    var secondString = str2.Substring(j, 2); // Extract a two-character substring from the second string

                    // Check if the extracted substrings from both strings are equal
                    if (firstString.Equals(secondString))
                        ctr++; // Increment the counter if the substrings are equal
                }
            }
            return ctr; // Return the total count of common two-character substrings
        }
    }
}

Sample Output:

1
1
2

Flowchart:

For more Practice: Solve these Related Problems:

Write a C# program to compare two strings and count all 3-length substrings at the same positions that match.
Write a C# program to compare two strings and count matching substrings where the first characters match and the lengths are equal.
Write a C# program to count the number of positions where the strings contain different characters but the ASCII difference is less than 3.
Write a C# program to count how many 2-character substrings in one string are reversed versions of those in another string.

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