poj 3130

import java.util.Scanner;public class POJ_3130 {static double x[], y[];static double tx[], ty[];static double txp[], typ[];static int num;static int tnum;static double a, b, c;public static void main(String[] args) {Scanner scan = new Scanner(System.in);while (true) {int n = scan.nextInt();if (n == 0)break;num = n;x = new double[100];y = new double[100];tx = new double[100];ty = new double[100];txp = new double[100];typ = new double[100];for (int i = 0; i < n; i++) {x[i] = scan.nextDouble();y[i] = scan.nextDouble();tx[i + 1] = x[i];ty[i + 1] = y[i];}x[n] = x[0];y[n] = y[0];tx[0] = tx[n];ty[0] = ty[n];tx[n + 1] = tx[1];ty[n + 1] = ty[1];for (int i = 0; i < n; i++) {a = y[i + 1] - y[i];      // 求直线  aX+bY+c=0  的参数a,b,cb = x[i] - x[i + 1];c = x[i + 1] * y[i] - x[i] * y[i + 1];solve();}if (num == 0)System.out.println("0");elseSystem.out.println("1");}}public static void solve() {tnum = 0;for (int i = 1; i <= num; i++) {if (sig(a * tx[i] + b * ty[i] + c) <= 0) {  // 在一侧txp[tnum] = tx[i];typ[tnum++] = ty[i];} else {                                    // 在另一侧if (sig(a * tx[i - 1] + b * ty[i - 1] + c) < 0)  //小于0才会有交点insert(tx[i - 1], ty[i - 1], tx[i], ty[i]);if (sig(a * tx[i + 1] + b * ty[i + 1] + c )< 0)insert(tx[i + 1], ty[i + 1], tx[i], ty[i]);}}num = tnum;                       //更新  num,tx,tyfor (int j = 1; j <= num; j++) {tx[j] = txp[j - 1];ty[j] = typ[j - 1];}tx[0] = tx[num];ty[0] = ty[num];tx[num + 1] = tx[1];ty[num + 1] = ty[1];}private static int sig(double d) {if(d<1e-10)return -1;else if(d>1e-10)return 1;return 0;}public static void insert(double x1, double y1, double x2, double y2) {  //求两直线交点  其中一条直线  已经表示成ax+by+c=0,  另一直线 是两个点double xx = Math.abs(a * x1 + b * y1 + c);double yy = Math.abs(a * x2 + b * y2 + c);txp[tnum] = (x1 * yy + x2 * xx) / (xx + yy);typ[tnum++] = (y1 * yy + y2 * xx) / (xx + yy);}}