import java.awt.*; import java.util.Random; public class PointInPolygon { public static int pointInPolygon(int qx, int qy, int[] x, int[] y) { int n = x.length; int cnt = 0; for (int i = 0, j = n - 1; i < n; j = i++) { if (y[i] == qy && (x[i] == qx || y[j] == qy && (x[i] <= qx || x[j] <= qx) && (x[i] >= qx || x[j] >= qx))) return 0; // boundary if ((y[i] > qy) != (y[j] > qy)) { long det = ((long) x[i] - qx) * ((long) y[j] - qy) - ((long) x[j] - qx) * ((long) y[i] - qy); if (det == 0) return 0; // boundary if ((det > 0) != (y[j] > y[i])) ++cnt; } } return cnt % 2 == 0 ? -1 /* exterior */ : 1 /* interior */; } static int pointInPolygon2(int qx, int qy, int[] x, int[] y) { double sumAngles = 0; for (int i = 0, j = x.length - 1; i < x.length; j = i++) { if (isCrossOrTouchIntersect(qx, qy, qx, qy, x[i], y[i], x[j], y[j])) return 0; long x1 = x[j] - qx; long y1 = y[j] - qy; long x2 = x[i] - qx; long y2 = y[i] - qy; sumAngles += Math.atan2(x1 * y2 - y1 * x2, x1 * x2 + y1 * y2); } return Math.abs(sumAngles) < 1e-9 ? -1 : 1; } static int pointInPolygon3(int qx, int qy, int[] x, int[] y) { Random rnd = new Random(); long x2 = rnd.nextInt(100_000_000) + 100_000_000; long y2 = rnd.nextInt(100_000_000) + 100_000_000; int cnt = 0; for (int i = 0, j = x.length - 1; i < x.length; j = i++) { if (isCrossOrTouchIntersect(qx, qy, qx, qy, x[i], y[i], x[j], y[j])) return 0; if (isCrossIntersect(qx, qy, x2, y2, x[i], y[i], x[j], y[j])) ++cnt; } return cnt % 2 == 0 ? -1 : 1; } // random test public static void main(String[] args) { for (int step = 0; step < 10_000; step++) { int n = rnd.nextInt(10) + 3; int range = 10; int[][] xy = getRandomPolygon(n, range, range); int[] x = xy[0]; int[] y = xy[1]; int qx = rnd.nextInt(3 * range) - range; int qy = rnd.nextInt(3 * range) - range; boolean res = new Polygon(x, y, n).contains(qx, qy); for (int i = 0, j = n - 1; i < n; j = i++) res |= isCrossOrTouchIntersect(qx, qy, qx, qy, x[i], y[i], x[j], y[j]); // apply fix int res1 = pointInPolygon(qx, qy, x, y); int res2 = pointInPolygon2(qx, qy, x, y); int res3 = pointInPolygon3(qx, qy, x, y); if (res == (res1 == -1) || res1 != res2 || res1 != res3) throw new RuntimeException(); } } static Random rnd = new Random(1); static int[][] getRandomPolygon(int n, int maxWidth, int maxHeight) { int[] x = new int[n]; int[] y = new int[n]; int[] p = new int[n]; while (true) { for (int i = 0; i < n; i++) { x[i] = rnd.nextInt(maxWidth); y[i] = rnd.nextInt(maxHeight); p[i] = i; } for (boolean improved = true; improved; ) { improved = false; for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { int[] p1 = p.clone(); reverse(p1, i, j); if (len(x, y, p) > len(x, y, p1)) { p = p1; improved = true; } } } } int[] tx = x.clone(); int[] ty = y.clone(); for (int i = 0; i < n; i++) { x[i] = tx[p[i]]; y[i] = ty[p[i]]; } boolean ok = true; for (int i = 0; i < n; i++) { long x1 = x[(i - 1 + n) % n] - x[i]; long y1 = y[(i - 1 + n) % n] - y[i]; long x2 = x[(i + 1) % n] - x[i]; long y2 = y[(i + 1) % n] - y[i]; ok &= x1 * y2 - x2 * y1 != 0 || x1 * x2 + y1 * y2 <= 0; } for (int i2 = 0, i1 = p.length - 1; i2 < p.length; i1 = i2++) for (int j2 = 0, j1 = p.length - 1; j2 < p.length; j1 = j2++) ok &= i1 == j1 || i1 == j2 || i2 == j1 || !isCrossOrTouchIntersect(x[i1], y[i1], x[i2], y[i2], x[j1], y[j1], x[j2], y[j2]); if (ok) return new int[][]{x, y}; } } // http://en.wikipedia.org/wiki/2-opt static void reverse(int[] p, int i, int j) { int n = p.length; // reverse order from i to j while (i != j) { int t = p[j]; p[j] = p[i]; p[i] = t; i = (i + 1) % n; if (i == j) break; j = (j - 1 + n) % n; } } static double len(int[] x, int[] y, int[] p) { double res = 0; for (int i = 0, j = p.length - 1; i < p.length; j = i++) { double dx = x[p[i]] - x[p[j]]; double dy = y[p[i]] - y[p[j]]; res += Math.sqrt(dx * dx + dy * dy); } return res; } static boolean isCrossOrTouchIntersect(long x1, long y1, long x2, long y2, long x3, long y3, long x4, long y4) { if (Math.max(x1, x2) < Math.min(x3, x4) || Math.max(x3, x4) < Math.min(x1, x2) || Math.max(y1, y2) < Math.min(y3, y4) || Math.max(y3, y4) < Math.min(y1, y2)) return false; long z1 = (x2 - x1) * (y3 - y1) - (y2 - y1) * (x3 - x1); long z2 = (x2 - x1) * (y4 - y1) - (y2 - y1) * (x4 - x1); long z3 = (x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3); long z4 = (x4 - x3) * (y2 - y3) - (y4 - y3) * (x2 - x3); return (z1 <= 0 || z2 <= 0) && (z1 >= 0 || z2 >= 0) && (z3 <= 0 || z4 <= 0) && (z3 >= 0 || z4 >= 0); } static boolean isCrossIntersect(long x1, long y1, long x2, long y2, long x3, long y3, long x4, long y4) { long z1 = (x2 - x1) * (y3 - y1) - (y2 - y1) * (x3 - x1); long z2 = (x2 - x1) * (y4 - y1) - (y2 - y1) * (x4 - x1); long z3 = (x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3); long z4 = (x4 - x3) * (y2 - y3) - (y4 - y3) * (x2 - x3); return (z1 < 0 || z2 < 0) && (z1 > 0 || z2 > 0) && (z3 < 0 || z4 < 0) && (z3 > 0 || z4 > 0); } }