二分查找——算法系列

二分查找有两个条件：

1. 数组必须有序，无序数组查找之前需要先让其有序
2. 只限于顺序存储结构

代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Net;
using System.Threading;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> list = new List<int>();
            for (int i = 0; i < 2000; i++)
            {
                Thread.Sleep(1);
                list.Add(new Random((int)DateTime.Now.Ticks).Next(0, 100));
            }
            list.OrderBy(single => single).ToList();
            for (int i = 0; i < 100; i++)
            {
                Thread.Sleep(100);
                if (BinarySearch(list, i) == 1)
                    Console.WriteLine("找到了");
                else
                    Console.WriteLine("没找到");
            }
            
            Console.ReadLine();
        }

        public static int BinarySearch(List<int> list, int key)
        {
            int low = 0;
            int high = list.Count - 1;
            while (low <= high)
            {
                int middle = (low + high) / 2;
                if (key == list[middle])
                    return 1;
                else if (key > list[middle])
                    low = middle + 1;
                else
                    high = middle - 1;
            }
            return 0;
        }
    }
}