Shanghai 2004 ( UVALive 3259) Amphiphilic Carbon Molecules

Link To The Problem

采用了枚举加扫描的方法，注意极角排序的方式。

知识点 ： 极角，叉积

Code:

// ShangHai 2004 (UValive 3529)// 知识点：极角排序，叉积#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>#include<vector>using namespace std;#define FOR(i,a,b) for(int (i)=(a);(i)<=(b);(i)++)#define DOR(i,a,b) for(int (i)=(a);(i)>=(b);(i)--)#define oo 1e6#define eps 1e-9#define nMax 5000//{#define pb push_back#define dbg(x) cerr << __LINE__ << ": " << #x << " = " << x << endl#define F first#define S second#define bug puts("OOOOh.....");#define zero(x) (((x)>0?(x):-(x))<eps)#define LL long long#define DB double #define sf scanf#define pf printf#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)double const pi = acos(-1.0);double inline sqr(double x) { return x*x; }int dcmp(double x){    if(fabs(x)<eps) return 0;    return x>0?1:-1;}//}// Describe of the 2_K Geomtry// First Part : Point and Line// Second Part Cicle// Third Part Polygan// First Part:// ****************************** Point and Line *******************************\\//{class point {public:    double x,y;    point (double x=0,double y=0):x(x),y(y) {}    void make(double _x,double _y) {x=_x;y=_y;}    void read() { scanf("%lf%lf",&x,&y); }    void out() { printf("%.2lf %.2lf\n",x,y);}    double len() { return sqrt(x*x+y*y); }    point friend operator - (point const& u,point const& v) {        return point(u.x-v.x,u.y-v.y);    }    point friend operator + (point const& u,point const& v) {        return point(u.x+v.x,u.y+v.y);    }    double friend operator * (point const& u,point const& v) {        return u.x*v.y-u.y*v.x;    }    double friend operator ^ (point const& u,point const& v) {        return u.x*v.x+u.y*v.y;    }    point friend operator * (point const& u,double const& k) {        return point(u.x*k,u.y*k);    }point friend operator / (point const& u,double const& k) { return point(u.x/k,u.y/k); }friend bool operator < (point const& u,point const& v){if(dcmp(v.x-u.x)==0) return dcmp(u.y-v.y)<0;return dcmp(u.x-v.x)<0;}friend bool operator != (point const& u,point const& v){return dcmp(u.x-v.x) || dcmp(u.y-v.y);}point rotate(double s) {return point(x*cos(s) + y*sin(s),\-x*sin(s) + y*cos(s));}};typedef class line{public:    point a,b;    line() {}    line (point a,point b):a(a),b(b){}    void make(point u,point v) {a=u;b=v;}    void read() { a.read(),b.read(); }}segment;double det(point u,point v) {return u.x*v.y - u.y*v.x;}double dot(point u,point v) {return u.x*v.x + u.y*v.y;}// Weather P is On the Segment (uv) int dot_on_seg(point p,point u,point v){return dcmp(det(p-u,v-p))==0 && dcmp(dot(p-u,v-p)) >= 0; // '>=' means P is u or v}// The distance from point p to line ldouble PToLine(point p,line l) {return fabs((p-l.a)*(l.a-l.b))/(l.a-l.b).len();}// The ProJect Of Point(p) To Line(l)point PointProjectLine(point p,line l) {double t = dot(l.b-l.a,p-l.a)/dot(l.b-l.a,l.b-l.a);return l.a + (l.b-l.a)*t;}//}// ****************************** First Part end ********************************\\// Second Part:// ********************************* Circle *************************************\\// {struct circle {point O;double r;circle() {};circle(point O,double r):O(O),r(r){};};//}// ****************************** Second Part End *******************************\\// Third Part :// ********************************* Polygan *************************************\\// {int ConvexHull(vector<point>& p){int n=p.size();int m=0;vector<point> q;q.resize(2*n+5);rep(i,n) {while(m>1 && dcmp((q[m-1]-q[m-2])*(p[i]-q[m-2])) <= 0) m--;q[m++] = p[i];}int k = m;for(int i=n-2;i>=0;i--) {while(m>k && dcmp((q[m-1]-q[m-2])*(p[i]-q[m-2])) <= 0) m--;q[m++] = p[i];}q.resize(m) ;if(m>1) q.resize(m-1);// p = q;    // 是否修改原来的多边形return q.size();}// 三角形重心point Center(point a,point b,point c){return (a+b+c)/3.0;}// Centroid of Polyganpoint Centroid(vector<point> p){point O(0,0),ret(0,0);int n = p.size();p.pb(p[0]);double area = 0.0;rep(i,n) {ret = ret + Center(O,p[i],p[i+1])*dot(p[i]-O,p[i+1]-O);area += dot(p[i]-O,p[i+1]-O);}if(dcmp(area)==0) {pf("There maybe something wrong\n");return p[0];}return ret / area;}struct Polygan{vector<point> g;Polygan() {};Polygan(vector<point> g):g(g){};Polygan(point p[],int n) {g.clear();rep(i,n) g.pb(p[i]); };int convex() { return ConvexHull(g); }point center() { return Centroid(g);  } // 多边形的重心};//}// ******************************* Third Part End ********************************\\// Sovle Partint n;point p[nMax],a[nMax];int in[nMax];int od[nMax],f[nMax];void adjust(point &u) {if(dcmp(u.x)==0) {if(u.y > 0) u.y = -u.y;}}inline int small(point u,point v) {  //极角排序if(dcmp(u.x)==0) return dcmp(v.x)!=0;if(dcmp(v.x)==0) return 0;return dcmp(u.y/u.x-v.y/v.x)<0;}inline int equal(point u,point v) {  //极角排序if(dcmp(u.x)==0 || dcmp(v.x)==0) return dcmp(u.x)==0 && dcmp(v.x)==0;return dcmp(u.y/u.x-v.y/v.x)==0;}int cmp(int i,int j) {return small(a[i],a[j]);}struct Event{int fr,en;int Count;point v;void make(point p,int a,int b,int c){fr = a;en = b;Count = c;v = p;if(v.x < 0) { v.x=-v.x,v.y=-v.y; }if(dcmp(v.x) == 0) { v.x = 0;if(v.y>0) v.y=-v.y; }}};Event event[nMax];int N;int on[nMax];void updata() {int i,j;int tmp = 0;N = 0;for(i=0;i<n-1;) {for(j=i+1;j<n-1;j++) if(!equal(a[od[j]],a[od[i]])) break;event[N].make(a[od[i]],i,j,j-i);N ++;i = j;}}int left(point p,point v) {return dcmp(p*v) < 0;}int deal(int cur){point s=p[cur];rep(i,n) od[i]=i;int k = 0;rep(i,n) if(i!=cur) {a[k] = p[i]-s;on[k++]=in[i];}sort(od,od+k,cmp);int w[2]={0};int b[2]={0};updata();//event[0].v.out();for(int i=event[0].en;i<k;i++) {if(left(event[0].v,a[od[i]])){if(on[od[i]]) b[0]++;else w[0]++;}else {if(on[od[i]]) b[1]++;else w[1]++;}}//pf("%d %d %d %d\n",b[0],b[1],w[0],w[1]);int ans = max(event[0].Count + b[0] + w[1] ,\  event[0].Count + b[1] + w[0]);for(int i=1;i<N;i++) {for(int j=event[i-1].fr;j<event[i-1].en;j++) {if(left(event[i].v,a[od[j]])) {if(on[od[j]]) b[0]++;else w[0]++;}else {if(on[od[j]]) b[1]++;else w[1]++;}}for(int j=event[i].fr;j<event[i].en;j++) {if(left(event[0].v,a[od[j]])) {if(on[od[j]]) b[0]--;else w[0]--;}else {if(on[od[j]]) b[1]--;else w[1]--;}}//pf("%d %d %d %d %d\n",b[0],b[1],w[0],w[1],event[i].Count);ans = max(ans,event[i].Count + b[0] + w[1]);ans = max(ans,event[i].Count + b[1] + w[0]);}return ans+1;}void work() {int ans = 0;rep(i,n) {ans = max(ans,deal(i));//dbg(ans);puts("");}pf("%d\n",ans);}int main() {#ifndef ONLINE_JUDGEfreopen("in.txt","r",stdin);#endifwhile(~sf("%d",&n),n){rep(i,n) {p[i].read(),sf("%d",&in[i]);}work();}return 0;}