C# - Array Programs and interview questions

Array Programs and Interview Questions for C#

Let's do some Hands on Array programming

a. Find Common Strings in Two String Arrays

Write a program to find common strings between two string arrays.

using System;
using System.Linq;

class Program
{
    static void Main()
    {
        string[] array1 = { "apple", "banana", "cherry" };
        string[] array2 = { "banana", "kiwi", "cherry" };

        var commonStrings = array1.Intersect(array2);

        Console.WriteLine("Common Strings: " + string.Join(", ", commonStrings));
    }
}

We can use Intersect between two arrays.

Find the String with the Most Vowels

Write a program to find the string with the most vowels in a string array.

using System;

class Program
{
    static void Main()
    {
        string[] words = { "apple", "banana", "cherry", "blueberry", "kiwi" };

        string mostVowels = words[0];
        int maxVowelCount = 0;

        foreach (string word in words)
        {
            int vowelCount = CountVowels(word);
            if (vowelCount > maxVowelCount)
            {
                maxVowelCount = vowelCount;
                mostVowels = word;
            }
        }

        Console.WriteLine($"String with Most Vowels: {mostVowels}");

        int CountVowels(string s)
        {
            int count = 0;
            foreach (char c in s.ToLower())
            {
                if ("aeiou".Contains(c)) count++;
            }
            return count;
        }
    }
}

Remove Duplicates from a String Array

Write a program to remove duplicates from a string array.

using System;
using System.Linq;

class Program
{
    static void Main()
    {
        string[] words = { "apple", "banana", "apple", "cherry", "banana", "kiwi" };

        string[] uniqueWords = words.Distinct().ToArray();

        Console.WriteLine("Unique Words: " + string.Join(", ", uniqueWords));
    }
}

Concatenate All Strings in a String Array

Write a program to concatenate all strings in a string array into a single string.

using System;

class Program
{
    static void Main()
    {
        string[] words = { "apple", "banana", "cherry", "blueberry", "kiwi" };

        string result = string.Join(" ", words);

        Console.WriteLine("Concatenated String: " + result);
    }
}

Find the Longest String in a String Array

Write a program to find the longest string in a string array.

using System;

class Program
{
    static void Main()
    {
        string[] words = { "apple", "banana", "cherry", "blueberry", "kiwi" };

        string longest = words[0];

        foreach (string word in words)
        {
            if (word.Length > longest.Length)
                longest = word;
        }

        Console.WriteLine($"Longest String: {longest}");
    }
}

Find Duplicate Elements in an Integer Array

Write a program to find duplicate elements in an array.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        int[] numbers = { 1, 2, 3, 1, 3, 6, 6 };

        var seen = new HashSet<int>();
        var duplicates = new HashSet<int>();

        foreach (int number in numbers)
        {
            if (!seen.Add(number))
                duplicates.Add(number);
        }

        Console.WriteLine("Duplicates: " + string.Join(", ", duplicates));
    }
}

Count the Frequency of Elements in an Array

Write a program to count the frequency of each element in an array.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        int[] numbers = { 1, 2, 2, 3, 4, 4, 4 };

        var frequency = new Dictionary<int, int>();

        foreach (int number in numbers)
        {
            if (frequency.ContainsKey(number))
                frequency[number]++;
            else
                frequency[number] = 1;
        }

        foreach (var kvp in frequency)
        {
            Console.WriteLine($"Number {kvp.Key}: {kvp.Value} times");
        }
    }
}

Find the Second Largest Element

Write a program to find the second largest element in an array.

using System;

class Program
{
    static void Main()
    {
        int[] numbers = { 10, 20, 4, 45, 99 };

        int max = int.MinValue;
        int secondMax = int.MinValue;

        foreach (int number in numbers)
        {
            if (number > max)
            {
                secondMax = max;
                max = number;
            }
            else if (number > secondMax && number != max)
            {
                secondMax = number;
            }
        }

        Console.WriteLine($"Second Largest: {secondMax}");
    }
}

Find the Largest and Smallest Element in an Array

Write a program to find the largest and smallest elements in an array.

using System;

class Program
{
    static void Main()
    {
        int[] numbers = { 3, 5, 7, 2, 8, -1, 4 };

        int max = numbers[0];
        int min = numbers[0];

        foreach (int number in numbers)
        {
            if (number > max)
                max = number;
            if (number < min)
                min = number;
        }

        Console.WriteLine($"Largest: {max}");
        Console.WriteLine($"Smallest: {min}");
    }
}