LA 4728 旋转卡壳算法求凸包的最大直径

#include<iostream>
#include<cstdio>
#include<cmath>
#include<vector>
#include<algorithm>
using namespace std;

struct Point {
	int x, y;
	Point(int x=0, int y=0):x(x),y(y) { }
};

typedef Point Vector;

Vector operator - (const Point& A, const Point& B) {
	return Vector(A.x-B.x, A.y-B.y);
}

int Cross(const Vector& A, const Vector& B) {
	return A.x*B.y - A.y*B.x;
}

int Dot(const Vector& A, const Vector& B) {
	return A.x*B.x + A.y*B.y;
}

int Dist2(const Point& A, const Point& B) {
	return (A.x-B.x)*(A.x-B.x) + (A.y-B.y)*(A.y-B.y);
}

bool operator < (const Point& p1, const Point& p2) {
	return p1.x < p2.x || (p1.x == p2.x && p1.y < p2.y);
}

bool operator == (const Point& p1, const Point& p2) {
	return p1.x == p2.x && p1.y == p2.y;
}

int max(int a,int b)
{
    return a>b?a:b;
}

vector<Point> ConvexHull(vector<Point>& p) //求凸包
{
	sort(p.begin(), p.end());
	p.erase(unique(p.begin(), p.end()), p.end());
	int i,n = p.size();
	int m = 0;
	vector<Point> ch(n+1);
	for(i = 0; i < n; i++) {
		while(m > 1 && Cross(ch[m-1]-ch[m-2], p[i]-ch[m-2]) <= 0) m--;
		ch[m++] = p[i];
	}
	int k = m;
	for(i = n-2; i >= 0; i--) {
		while(m > k && Cross(ch[m-1]-ch[m-2], p[i]-ch[m-2]) <= 0) m--;
		ch[m++] = p[i];
	}
	if(n > 1) m--;
	ch.resize(m);
	return ch;
}

int diameter2(vector<Point>& points)//求凸包的最大直径（旋转卡壳算法）
{
    vector<Point> p = ConvexHull(points);
    int n = p.size();
    if(n == 1) return 0;
    if(n == 2) return Dist2(p[0], p[1]);
    p.push_back(p[0]);
    int ans = 0;
    int i=0,j=1;
    for(;i<n;i++)
    {
        while(Cross(p[i+1]-p[i], p[j+1]-p[i]) > Cross(p[i+1]-p[i], p[j]-p[i]))
            j=(j+1)%n;
        ans=max(ans,max(Dist2(p[i],p[j]),Dist2(p[i+1],p[j+1])));
    }
    return ans;
}

int main()
{
    int T,i,n,x,y,w;
    vector<Point> P;
    scanf("%d",&T);
    while(T--)
    {
        P.clear();
        scanf("%d",&n);
        for(i=0;i<n;i++)
        {
            scanf("%d%d%d", &x, &y, &w);
            P.push_back(Point(x, y));
            P.push_back(Point(x+w, y));
            P.push_back(Point(x, y+w));
            P.push_back(Point(x+w, y+w));
        }
        printf("%d\n", diameter2(P));
    }
    return 0;
}