Find the second maximum number in an array with the smallest complexity

You could sort the array and choose the item at the second index, but the following O(n) loop will be much faster.

int[] myArray = new int[] { 0, 1, 2, 3, 13, 8, 5 };
int largest = int.MinValue;
int second = int.MinValue;
foreach (int i in myArray)
{
 if (i > largest)
 {
  second = largest;
  largest = i;
 }
else if (i > second)
    second = i;
}

System.Console.WriteLine(second);

OR

Try this (using LINQ):

int secondHighest = (from number in test
                             orderby number descending
                             select number).Distinct().Skip(1).First()

How to get the second highest number in an array in Visual C#?

public static int F(int[] array)
{
    array = array.OrderByDescending(c => c).Distinct().ToArray();
    switch (array.Count())
    {
        case 0:
            return -1;
        case 1:
            return array[0];
    }
    return array[1];
}

Answer in C# :

static void Main(string[] args)
        {
            //let us define array and vars
            var arr = new int[]{ 100, -3, 95,100,95, 177,-5,-4,177,101 };

            int biggest =0, secondBiggest=0;
            for (int i = 0; i < arr.Length; ++i)
                {
                int arrItem = arr[i];
                if(arrItem > biggest)
                {
                    secondBiggest = biggest; //always store the prev value of biggest 
                                             //to second biggest...
                    biggest = arrItem;
                 }
                else if (arrItem > secondBiggest && arrItem < biggest) //if in our 
                 //iteration we will find a number that is bigger than secondBiggest and smaller than biggest 
                   secondBiggest = arrItem;
            }

            Console.WriteLine($"Biggest Number:{biggest}, SecondBiggestNumber: 
                              {secondBiggest}");
            Console.ReadLine(); //make program wait
        }

Output : Biggest Number:177, SecondBiggestNumber:101