C# - String Interview Questions

String Operations in C#

1. Check if a String is a Palindrome

Write a method to check if a string is a palindrome.

public static bool IsPalindrome(string input)
{
    int left = 0;
    int right = input.Length - 1;
    
    while (left < right)
    {
        if (input[left] != input[right])
            return false;
        left++;
        right--;
    }
    return true;
}

// Example usage:
bool isPalindrome = IsPalindrome("radar"); // true
bool isPalindrome2 = IsPalindrome("hello"); // false

2. Count the Number of Vowels in a String

Write a method to count the number of vowels in a string.

public static int CountVowels(string input)
{
    int count = 0;
    string vowels = "aeiouAEIOU";
    foreach (char c in input)
    {
        if (vowels.Contains(c))
            count++;
    }
    return count;
}

// Example usage:
int vowelCount = CountVowels("hello world"); // 3

3.Reverse a String

public static string ReverseString(string input)
{
    char[] charArray = input.ToCharArray();
    Array.Reverse(charArray);
    return new string(charArray);
}

// Example usage:
string reversed = ReverseString("hello"); // "olleh"

4. Reverse Each Word in a String

public static string ReverseEachWord(string input)
{
    string[] words = input.Split(' ');
    for (int i = 0; i < words.Length; i++)
    {
        char[] charArray = words[i].ToCharArray();
        Array.Reverse(charArray);
        words[i] = new string(charArray);
    }
    return string.Join(" ", words);
}

// Example usage:
string reversedWords = ReverseEachWord("hello world"); // "olleh dlrow"