codeforces 113 166B 凸包 计算几何

判断一个多边形能否放进凸包中

对所有点再做一次凸包，把重点和共线点都加进凸包集合中

如果图暴集合中有某个点是多边形的点就输出no

else yes

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
typedef __int64 lld;
const double eps = 1e-8;
const double pi = acos(-1.0);
struct Point {
    lld x, y;
    int id;
    bool operator == (const Point& t) const {
        return x==t.x && y==t.y;
    }
}GP,p[1000010]; 
inline lld Cross(Point a, Point b, Point c) {                    // 叉积
    return (b.x-a.x)*(c.y-a.y) - (c.x-a.x)*(b.y-a.y); 
}
bool cmpyx(Point a, Point b) {                                        
    if ( a.y != b.y )
        return a.y < b.y;
    return a.x < b.x;
}
void Grahamxy(Point *p, int &n) {                                    // 水平序(住:两倍空间)
    if ( n < 3 ) 
        return;
    int i, m=0, top=1;
//    sort(p, p+n, cmpyx);    
    for (i=n; i < 2*n-1; i++)
        p[i] = p[2*n-2-i];
    for (i=2; i < 2*n-1; i++) {
        while ( top > m && Cross(p[top], p[i], p[top-1]) < 0 ) 
            top--;
        p[++top] = p[i];
        if ( i == n-1 )    m = top;
    }
    n = top;
}
int main(){
     int n,m,i,j;
     scanf("%d",&n);
     for(i=0;i<n;i++)
         scanf("%I64d%I64d",&p[i].x,&p[i].y); p[i].id=1;
     scanf("%d",&m);
     for(i=0;i<m;i++)
         scanf("%I64d%I64d",&p[i+n].x,&p[i+n].y);p[i+n].id=-1;
     n=n+m;
     sort(p,p+n,cmpyx);
     Grahamxy(p,n);
     for(i=1;i<=n;i++) {
            if(p[i].id<0){
                printf("NO\n");
                return 0;
            }
     }
     printf("YES\n");
     return 0;
}