"POJ" 1279

http://poj.org/submit?problem_id=1279

Test instructions: To an n-point polygon, n<=1500, to see the area of points on all polygons within the polygon.

#include <cstdio> #include <cstring> #include <cmath> #include <string> #include <iostream > #include <algorithm> #include <queue> #include <set> #include <map>using namespace std; typedef long Long LL; #define REP (i, n) for (int i=0; i< (n); ++i) #define FOR1 (i,a,n) for (int i= (a); i<= (n); ++i) #define For2 (i,a,n) for (int i= (a);i< (n), ++i) #define FOR3 (i,a,n) for (int i= (a); i>= (n); i.) #define FOR4 (i,a,n) for (int i= ( a);i> (n); i) #define CC (i,a) memset (i,a,sizeof (i)) #define READ (a) a=getint () #define PRINT (a) printf ("%d", a) # Define DBG (x) cout << (#x) << "=" << (x) << endl#define error (x) (! x) puts ("error"): 0) #define RDM (x, i) for (int i=ihead[x]; i; i=e[i].next) inline const int Getint () {int r=0, k=1; Char c=g Etchar (); for (; c< ' 0 ' | | C> ' 9 '; C=getchar ()) if (c== '-') k=-1; for (; c>= ' 0 ' &&c<= ' 9 '; C=getchar ()) r=r*10+c-' 0 '; return k*r; }const double eps=1e-6;const int n=1515;int dcmp (double x) {return ABS (x) <eps?0: (x<0?-1:1); }struct IP {double x, y; IP (double _x=0, double _y=0): X (_x), Y (_y) {}};typedef IP iv;iv operator-(IP A, IP b) {Retu RN IV (a.x-b.x, A.Y-B.Y); }IP operator + (IP A, IV b) {return IP (a.x+b.x, a.y+b.y);} IV operator * (IP A, double D) {return IV (A.x*d, a.y*d);} Double Cross (iv A, IV b) {return a.x*b.y-a.y*b.x;} Double angle (IV &a) {return atan2 (A.Y, a.x);} struct IL {iV v; IP p;double ang;void Set (IP A, IP b) {p=a; v=b-a; Ang=angle (v);} BOOL operator< (const IL &b) const {return ang<b.ang;}}; IP LLi (Il &a, il &b) {static IV u;static double T;u=a.p-b.p;t=cross (B.V, u)/cross (A.V, B.V); return a.p+a.v*t;} BOOL OnL (IP &a, IL &l) {return dcmp (cross (L.V, A-L.P)) >0;} BOOL Half (IL *line, int n, IP *s, int &cnt) {static IL a[n], q[n];static iP b[n];static int front, tail;memcpy (A, line , sizeof (IL) * (n+1)), sort (a+1, a+1+n), Q[front=tail=0]=a[1];for1 (i, 2, N) {while (Front!=tail &&!onl (B[tail-1], A[i])--tail;while(Front!=tail &&!onl (B[front], a[i]) ++front;q[++tail]=a[i];if (dcmp (Cross (Q[TAIL-1].V, Q[TAIL].V)) ==0) {-- Tail;if (OnL (A[I].P, Q[tail])) q[tail]=a[i];} if (front!=tail) B[tail-1]=lli (Q[tail], q[tail-1]);} while (Front!=tail &&!onl (B[tail-1], Q[front])--tail;if (tail-front<=1) return 0;cnt=0;b[tail]=lli (q[ Tail], Q[front]); For1 (i, Front, tail) S[++cnt]=b[i];return 1;} IL Line[n];ip a[n], B[n];int Ln, N, num, flag;void Add (IP A, IP b) {++ln; Line[ln].set (A, b);} void CLR () {num=ln=0;} void Readin () {read (n); For1 (i, 1, N) scanf ("%lf%lf", &a[i].x, &AMP;A[I].Y);} void Build () {A[n+1]=a[1];for1 (i, 1, N) Add (a[i+1], a[i]);} void work () {Flag=half (line, LN, b, num);} void Getans () {if (!flag) {puts ("0.00");} Double Ans=0;b[num+1]=b[1];for1 (i, 1, num) ans+=b[i].x*b[i+1].y-b[i].y*b[i+1].x;printf ("%.2f\n", ANS/2);} int main () {int ta=getint (), while (ta--) {clr (), Readin (); build (); work (); Getans ();} return 0;}

　　

Bare half-plane sex ....... .....

"POJ" 1279