C#二分查找算法实例分析

原文链接：https://www.jb51.net/article/65006.htm

internal class Program
{
    static void Main(string[] args)
    {
        Program program = new Program();

        int[] ints = { 1, 2, 3, 4, 5 };
        int i = program.BinarySearch(ints, 3);
        Console.WriteLine(i);
        Console.ReadKey();


    }

    public int[] GetSubArray(int[] arr, int start, int end)
    {
        List<int> ints = new List<int>();
        for (int i = start; i <= end; i++)
        {
            ints.Add(arr[i]);
        }
        return ints.ToArray();
    }

    public int BinarySearch(int[] arr, int x)
    {
        if (arr.Length == 0)
        {
            return -1;
        }
        int mid = arr.Length / 2;
        if (arr[mid] == x)
        {
            return mid;
        }
        if (x < arr[mid])
        {
            return BinarySearch(GetSubArray(arr, 0, mid - 1), x);
        }
        else
        {
            int indexFound = BinarySearch(GetSubArray(arr, mid + 1, arr.Length - 1), x);
            if (indexFound == -1)
            {
                return -1;
            }
            else
            {
                return mid + 1 + BinarySearch(GetSubArray(arr, mid + 1, arr.Length - 1), x);
            }
        }
    }
}