网格

#define abs(x) ((x)>0?(x):-(x))struct point{int x,y;};int gcd(int a,int b){    return b?gcd(b,a%b):a;}//多边形上的网格点个数int grid_onedge(int n,point* p){    int i,ret=0;    for (i=0;i<n;i++)        ret+=gcd(abs(p[i].x-p[(i+1)%n].x),abs(p[i].y-p[(i+1)%n].y));    return ret;}//多边形内的网格点个数int grid_inside(int n,point* p){    int i,ret=0;    for (i=0;i<n;i++)        ret+=p[(i+1)%n].y*(p[i].x-p[(i+2)%n].x);    return (abs(ret)-grid_onedge(n,p))/2+1;}