（第二章）分治法

二分搜索技术

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
template<class Type>
int BinarySearch(Type a[],const Type &x,int n)
{
    int left=0;int right=n-1;
    while(left<=right)
    {
        int middle=(left+right)/2;
        if(x==a[middle])
            return middle;
        if(x>a[middle])
            left=middle+1;
        else
            right=middle-1;
    }
    return -1;
}
int main()
{
    int n;
    int a[100];
    while(cin>>n)
    {
        for(int i=0;i<n;++i)
            cin>>a[i];

        sort(a,a+n);
        int f;
        cin>>f;
        int dir=BinarySearch(a,f,n);
        cout<<dir<<endl;
    }
}

大整数的乘法