c#算法

1.二分查找

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5 using System.Threading.Tasks;
 6 
 7 namespace list
 8 {
 9     class Program
10     {
11 
12         public static int BinarySearch(List<int> intList, int target)
13         {
14             //int? n = null;
15             int low = 0;
16             int high = intList.Count - 1;
17             
18             while(low<=high)
19             {
20                 int mid = (low + high) / 2;
21                 if (intList[mid] == target)
22                     return mid;
23                 else if (intList[mid] > target)
24                     high = mid-1;
25                 else
26                     low = mid+1;
27             }
28             
29             return -999999;
30         }
31 
32         static void Main(string[] args)
33         {
34             
35 
36             List<int> list = new List<int>();
37             for (int i = 1; i < 10; i++)
38                 list.Add(i);
39            
40             int a=BinarySearch(list,1);
41             int b = list[a];
42 
43             Console.WriteLine("a.Index="+a+" , a.Value= "+b );
44             Console.ReadKey();
45         }
46     }
47 }

BinarySearch