zoj 1760 查找

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

撸了个二分查找

#include<iostream>
#include<cmath>
#include<iomanip>
#include<algorithm>
using namespace std;

int bs(int a[],int n,int len)
{
          int lo = 0,hi = len-1,mid = (lo+hi)/2;
          while(lo<=hi)
          {
                    if(n<a[mid])
                    {
                              hi = mid -1;
                              mid = (lo+hi)/2;
                    }
                    else if(n>a[mid])
                    {
                              lo = mid +1;
                              mid = (lo+hi)/2;
                    }
                    else
                              return mid;
          }
          if(lo>hi)
                    return -1;
}


int main()
{
          int a[10000];
          int x;
          while(cin>>x && x!=-1)
          {
                    int i = 1;
                    a[0] = x;
                    while(cin>>a[i])
                    {
                              if(a[i]==0)
                                        break;
                              i++;
                    }
                    sort(a,a+i);
                    int count = 0;
                    for(int j = i-1;j>=0;j--)
                    {
                              if(bs(a,a[j]*2,i)!=-1)
                              {
                                        count++;
                              }
                    }
                    cout<<count<<endl;


          }
}