标签:|| can its poi style main \n using const
凸包 + 旋转卡壳 模本
c++ code:
#include <bits/stdc++.h> using namespace std; const int N=3e5+7; struct point{ double x, y; point(){} point(double x, double y) : x(x), y(y) {} friend point operator + (const point &a, const point &b){ return point(a.x + b.x, a.y + b.y); } friend point operator - (const point &a, const point &b){ return point(a.x - b.x, a.y - b.y); } friend point operator * (const point &a, const double &b){ return point(a.x * b, a.y * b); } friend point operator / (const point &a, const double &b){ return point(a.x / b, a.y / b); } friend bool operator == (const point &a, const point &b){ return a.x == b.x && a.y == b.y; } }; double r; double dis(point a,point b) { return sqrt((a.x-b.x)*(a.x-b.x)*1.0+(a.y-b.y)*(a.y-b.y)); } double cross(point a,point b,point c) //计算叉乘 { return (c.x - a.x) * (b.y - a.y) - (b.x - a.x) * (c.y - a.y); } double det(point a, point b) { return a.x * b.y - a.y * b.x; } double dot(point a, point b) { return a.x * b.x + a.y * b.y; } struct polygon_convex { vector<point> p; polygon_convex(int size = 0){ p.resize(size); } }; bool comp_less(const point &a, const point &b) { return a.x - b.x < 0 || a.x - b.x == 0 && a.y - b.y < 0; } polygon_convex convex_hull(vector<point> a) { polygon_convex res(2 * a.size() + 5); sort(a.begin(), a.end(), comp_less); a.erase(unique(a.begin(), a.end()), a.end()); int m = 0; for(int i = 0; i < a.size(); i ++){ while(m > 1 && det(res.p[m - 1] - res.p[m - 2], a[i] - res.p[m - 2]) <= 0) -- m; res.p[m ++] = a[i]; } int k = m; for(int i = int(a.size()) - 2; i >= 0; i --){ while(m > k && det(res.p[m - 1] - res.p[m - 2], a[i] - res.p[m - 2]) <= 0) -- m; res.p[m ++] = a[i]; } res.p.resize(m); if(a.size() > 1) res.p.resize(m - 1); return res; } polygon_convex a; point p[N]; double rotating_caliper(point *p,int n) { int j=1; r=2*r; p[n]=p[0]; for (int i=0;i<n;i++) { while (cross(p[i],p[i+1],p[j+1])-cross(p[i],p[i+1],p[j])<=0) j=(j+1)%n; r=min(r,fabs(cross(p[i],p[i+1],p[j]))/dis(p[i],p[i+1])); } return r; } int main() { int n; scanf("%d%lf",&n,&r); point node; for(int i=0;i<n;i++) { scanf("%lf%lf",&node.x,&node.y); a.p.push_back(node); } a=convex_hull(a.p); n=a.p.size(); for(int i=0;i<n;i++) p[i]=a.p[i]; if(n<=2) printf("0.000000000000\n"); else printf("%.12lf\n",rotating_caliper(p,n)); return 0; }
标签:|| can its poi style main \n using const
原文地址:https://www.cnblogs.com/lemon-jade/p/8977977.html