旋轉卡殼 求最遠點對

struct point{int x,y;point(){}point(int xx,int yy){x=xx;y=yy;}point operator-(point const &b)const{return point(x-b.x,y-b.y);}int friend operator*(point a,point b){return f_abs(a.x*b.y-a.y*b.x);}int len2(){return x*x+y*y;}};/*==================================================*\| rotating_calipers 旋轉卡殼 O(N)| CALL: res = graham(pnt, n); res為最遠點距離平方;\*==================================================*/int rotating_calipers(point pnt[],int n){    int q=1,ans=0,i;    for(i=0;i<n;i++){        while( (pnt[(i+1)%n]-pnt[i])*(pnt[(q+1)%n]-pnt[i])>(pnt[(i+1)%n]-pnt[i])*(pnt[q]-pnt[i]))q=(q+1)%n;        ans=f_max(ans , f_max((pnt[i]-pnt[q]).len2(),(pnt[(i+1)%n]-pnt[(q+1)%n]).len2()));    }    return ans;}