二分查找法

 

//　地址空间从０开始到8０００结束 步长为8
            int position = 8000;
            int number = int.Parse(txtNumber.Text);
            int[] numbers = new int[position];
            for(int i=0;i<position;i++)
            {
                numbers[i] = i;
            }
            int offset = 8;
            long low = 0;
            long high = position - offset;
            long mid = 0;
            string sign = "没有找到";
            while(low <= high)
            {
                mid = (low + high)/2;
                if (mid % 2 != 0) //这边不能为步长//步长为1的时候不需要这个
                {
                    mid = (low + high - offset)/2;//减一个步长肯定是合适的．
                }
                if (numbers[mid] == number)
                {
                    sign = mid.ToString() + "找到:";
                    break;
                }
                if (numbers[mid] > number)
                {
                    high = mid - offset;    
                }
                if (numbers[mid] < number)
                {
                    low = mid + offset;
                }
                
            }
            txtHTML.Text = sign;

   

//另一种方法
            long position;
            long low = 0;
            long high = 5000;//表示有多少个这样步长,如果是地址应该是 5000*8
            long mid = 0;
            int offset = 8;
            string sign = "没有找到";
            while(low <= high)
            {
                mid = (low + high)/2;
                if (numbers[mid] == number)
                {
                    int find =  (mid * offset) + position;
                    sign = find.ToString();
                    break;
                }
                if (numbers[mid] > number)
                {
                    high = (mid - 1)  * offset + position;    
                }
                if (numbers[mid] < number)
                {
                    low = (mid + 1) * offset + position;
                }
                
            }
            txtHTML.Text = sign;