简单几何(凸包) POJ 2187 Beauty Contest-白红宇

简单几何(凸包) POJ 2187 Beauty Contest

阅读量：6584 次

发布时间：2019-06-24

本文共 2906 字，大约阅读时间需要 9 分钟。

题意：求两点的距离平方的最大值

分析：凸包模板题

/************************************************* Author        :Running_Time* Created Time  :2015/10/25 9:31:11* File Name     :A.cpp ************************************************/#include 
     
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                      using namespace std;#define lson l, mid, rt << 1#define rson mid + 1, r, rt << 1 | 1typedef long long ll;const int N = 5e4 + 10;const int INF = 0x3f3f3f3f;const double EPS = 1e-10; int dcmp(double x) { //三态函数，减少精度问题 if (fabs (x) < EPS) return 0; else return x < 0 ? -1 : 1; } struct Point { //点的定义 double x, y; Point (double x=0, double y=0) : x (x), y (y) {} Point operator + (const Point &r) const { //向量加法 return Point (x + r.x, y + r.y); } Point operator - (const Point &r) const { //向量减法 return Point (x - r.x, y - r.y); } Point operator * (double p) { //向量乘以标量 return Point (x * p, y * p); } Point operator / (double p) { //向量除以标量 return Point (x / p, y / p); } bool operator < (const Point &r) const { //点的坐标排序 return x < r.x || (x == r.x && y < r.y); } bool operator == (const Point &r) const { //判断同一个点 return dcmp (x - r.x) == 0 && dcmp (y - r.y) == 0; } }; typedef Point Vector; //向量的定义 Point read_point(void) { //点的读入 double x, y; scanf ("%lf%lf", &x, &y); return Point (x, y); } double polar_angle(Vector A) { //向量极角 return atan2 (A.y, A.x); } double dot(Vector A, Vector B) { //向量点积 return A.x * B.x + A.y * B.y; } double cross(Vector A, Vector B) { //向量叉积 return A.x * B.y - A.y * B.x; } double length(Vector A) { //向量长度，点积 return sqrt (dot (A, A)); } double angle(Vector A, Vector B) { //向量转角，逆时针，点积 return acos (dot (A, B) / length (A) / length (B)); } double area_triangle(Point a, Point b, Point c) { //三角形面积，叉积 return fabs (cross (b - a, c - a)) / 2.0; } Vector rotate(Vector A, double rad) { //向量旋转，逆时针 return Vector (A.x * cos (rad) - A.y * sin (rad), A.x * sin (rad) + A.y * cos (rad)); } Vector nomal(Vector A) { //向量的单位法向量 double len = length (A); return Vector (-A.y / len, A.x / len); } Point point_inter(Point p, Vector V, Point q, Vector W) { //两直线交点，参数方程 Vector U = p - q; double t = cross (W, U) / cross (V, W); return p + V * t; } vector
                      
                        convex_hull(vector
                       
                         &P) { sort (P.begin (), P.end ()); int n = P.size (), k = 0; vector
                        
                          ret (n * 2); for (int i=0; i
                         
                           1 && cross (ret[k-1] - ret[k-2], P[i] - ret[k-1]) <= 0) k--; ret[k++] = P[i]; } for (int i=n-2, t=k; i>=0; --i) { while (k > t && cross (ret[k-1] - ret[k-2], P[i] - ret[k-1]) <= 0) k--; ret[k++] = P[i]; } ret.resize (k-1); return ret;}vector
                          
                            p;int main(void) { int n; while (scanf ("%d", &n) == 1) { p.clear (); for (int i=0; i
                           
                             qs = convex_hull (p); double ans = 0; for (int i=0; i