Check if a string is a palindrome in C#

A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward. In other words, it remains unchanged when its characters are reversed. Palindromes can be found in various contexts, including words, sentences, numbers, and even entire verses or paragraphs.

Few examples of palindromes:

1. Words: "radar", "level", "noon", "deified"
2. Phrases: "A man, a plan, a canal, Panama", "Madam, in Eden, I'm Adam"
3. Numbers: 121, 1331, 1221
4. Sentences: "Able was I ere I saw Elba", "Was it a car or a cat I saw?"

In general, when determining if a sequence is a palindrome, spaces, punctuation, and character case are often ignored. The focus is on the sequence of characters themselves, ensuring that when read backward, they form the same sequence as when read forward.

using System;

class Program
{
    // Entry point of the program
    internal static void Main(string[] args)
    {
        // Test cases
        string str1 = "radar";
        string str2 = "hello";

        // Check if the strings are palindromes
        checkPalindrome(str1); // Output: Palindrome
        checkPalindrome(str2); // Output: Not Palindrome
    }

    // Method to check if a string is a palindrome
    static void checkPalindrome(string str)  
    {  
        bool flag = true;  // Initialize flag as true initially
        
        // Loop through the string from both ends towards the middle
        for (int i = 0, j = str.Length - 1;  i < str.Length / 2; i++, j--)  
        {  
            // Compare characters from both ends
            if (str[i] != str[j])  
            {  
                flag = false;  // Set flag to false if characters don't match
                break;  // Break the loop as we already found a mismatch
            }  
        }  

        // Print the result based on the value of the flag
        if (flag)  
        {  
            Console.WriteLine("Palindrome");  // If flag is true, it's a palindrome
        }  
        else  
        {
            Console.WriteLine("Not Palindrome");  // If flag is false, it's not a palindrome
        }
    }
}

Explanation:

• The Main method serves as the entry point of the program.
• Two test cases (str1 and str2) are created with strings "radar" and "hello" respectively.
• The checkPalindrome method is called for each test case to determine if the strings are palindromes.
• The checkPalindrome method checks whether a given string is a palindrome or not.
• It iterates through the string from both ends towards the middle, comparing characters.
• If a pair of characters doesn't match, the method sets a boolean flag to false and breaks the loop.
• After the loop, it prints "Palindrome" if the flag is true, indicating the string is a palindrome; otherwise, it prints "Not Palindrome".