BinarySearch example

using System;
using System.Linq;

namespace BinarySearchExamples
{
    class Program
    {
        static void Main(string[] args)
        {

            int[] binarySearchTestArray = { 1, 2, 3, 5 };

            //For return of BinarySearch method see:
            //http://msdn.microsoft.com/en-us/library/w4e7fxsh.aspx



            //Examples of searched values that are not found.
            #region
            //I. Index of element that is in between the smallest and the largest item
            //but not found in the list.
            int searchedValue = 4;
            int indexOfSearchedValue = Array.BinarySearch(binarySearchTestArray, searchedValue);

            //The index of the next larger value is 3 (11) its bitwise complement is -4.
            //(Due to Two`s complement) See: http://en.wikipedia.org/wiki/Two%27s_complement
            // and http://stackoverflow.com/questions/791328/how-does-the-bitwise-complement-operator-work
            Console.WriteLine(indexOfSearchedValue);



            //II. Index of element that is smaller than the smallest element
            searchedValue = 0;
            indexOfSearchedValue = Array.BinarySearch(binarySearchTestArray, searchedValue);

            //Again the bitwise complement of first larger element is returned
            Console.WriteLine(indexOfSearchedValue);



            //III. Index of element that is larger than the largest element
            searchedValue = 454;
            indexOfSearchedValue = Array.BinarySearch(binarySearchTestArray, searchedValue);

            //This time the bitwise complement of elements count is returned
            //count =4 => -5
            Console.WriteLine(indexOfSearchedValue);
            #endregion



            //HOW TO FIND LARGEST THAT IS SMALLER THAN SEARCHED VALUE?
            searchedValue = 4;
            indexOfSearchedValue = Array.BinarySearch(binarySearchTestArray, searchedValue);

            //negate(to get index of first larger) and extract 1
            indexOfSearchedValue = ~indexOfSearchedValue - 1;

            Console.WriteLine("Index of searched value: {0}",indexOfSearchedValue);

            //Note: In case searched value is found just return its index
        }
    }
}