binarysearch.cs

using System;
using System.Text;
 
 
namespace BinarySearch
{
    class Program
    {
        static void Main(string[] args)
        {
 
 
 
            int[] A = { 1, 2, 3, 4, 5, 6 ,7,8,9};
            int K = 9; //item to search
 
            int pos=BinarySearch(A, K);
            if(pos==-1){
                  Console.WriteLine("Item "+ K + " not found");
            }else{
                  Console.WriteLine("Item "+ K + " found at " + pos);
            }
 
            Console.ReadLine();
 
        }
        static int BinarySearch(int[] A, int K)
        {
 
            int n = A.Length;
            int l = 0;
            int r = n - 1;
 
            while (l <= r)
            {
                int m = ((l + r) / 2);
                if (K == A[m])
                {
                    return m;
                }
                else if (K < A[m])
                {
                    r = m - 1;
                }
                else
                {
                    l = m + 1;
                }
 
            }
            return -1;
        }
    }
}