二分法模板

int n,k;  
const int maxn=1000;  
int a[maxn];  
void solve()  
{  
    int lb=-1,ub=n;  
    while(ub-lb>1)  
    {  
        int mid=(lb+ub)/2;  
        if(a[mid]>=k)  
            ub=mid;  
        else  
            lb=mid;  
    }  
    printf("%d",ub);  
}