zoj 1760 查找

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=760

撸了个二分查找

 1 #include<iostream>
 2 #include<cmath>
 3 #include<iomanip>
 4 #include<algorithm>
 5 using namespace std;
 6
 7 int bs(int a[],int n,int len)
 8 {
 9           int lo = 0,hi = len-1,mid = (lo+hi)/2;
10           while(lo<=hi)
11           {
12                     if(n<a[mid])
13                     {
14                               hi = mid -1;
15                               mid = (lo+hi)/2;
16                     }
17                     else if(n>a[mid])
18                     {
19                               lo = mid +1;
20                               mid = (lo+hi)/2;
21                     }
22                     else
23                               return mid;
24           }
25           if(lo>hi)
26                     return -1;
27 }
28
29
30 int main()
31 {
32           int a[10000];
33           int x;
34           while(cin>>x && x!=-1)
35           {
36                     int i = 1;
37                     a[0] = x;
38                     while(cin>>a[i])
39                     {
40                               if(a[i]==0)
41                                         break;
42                               i++;
43                     }
44                     sort(a,a+i);
45                     int count = 0;
46                     for(int j = i-1;j>=0;j--)
47                     {
48                               if(bs(a,a[j]*2,i)!=-1)
49                               {
50                                         count++;
51                               }
52                     }
53                     cout<<count<<endl;
54
55
56           }
57 }