【jzoj5247】【NOIP2017提高A组模拟8.10】【计算几何】【二分答案】

题目大意

解题思路

对点排序后显然满足二分性，手推一下就可判断是否相交。

code

#include
#include
#include
#include
#define LF double
#define LL long long
#define ULL unsigned int
#define fo(i,j,k) for(int i=j;i<=k;i++)
#define fd(i,j,k) for(int i=j;i>=k;i--)
#define fr(i,j) for(int i=begin[j];i;i=next[i])
using namespace std;
int const mn=1e5+9;
int n,m,a[mn],b[mn];
int cross(int x,int y,int a,int b){
    return (x>=a)||(y+1e-6>=1.0*b/a*(a-x));
}
int main(){
    freopen("d.in","r",stdin);
    freopen("d.out","w",stdout);
    scanf("%d",&n);
    fo(i,1,n)scanf("%d",&a[i]);
    fo(i,1,n)scanf("%d",&b[i]);
    sort(a+1,a+n+1);
    sort(b+1,b+n+1);
    scanf("%d",&m);
    fo(i,1,m){
        int x,y;
        scanf("%d%d",&x,&y);
        int l=1,r=n;
        while(l!=r){
            int md=(l+r+1)/2;
            if(cross(x,y,a[md],b[md]))l=md;
            else r=md-1;
        }
        if(!cross(x,y,a[l],b[l]))printf("0\n");
        else printf("%d\n",l);
    }
    return 0;
}