解题报告-HDU 3662 (三维凸包)

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#include <iostream>#include <cstring>#include <algorithm>#include <cstdio>#include <string>#include <vector>#include <queue>#include <cmath>using namespace std;#define eps 1e-7#define MAXV 310struct pt {double x, y, z;pt() {}pt(double _x, double _y, double _z) :x(_x), y(_y), z(_z) {}pt operator -(const pt p1) {return pt(x - p1.x, y - p1.y, z - p1.z);}pt operator *(pt p) {return pt(y * p.z - z * p.y, z * p.x - x * p.z, x * p.y - y * p.x);}double operator ^(pt p) {return x * p.x + y * p.y + z * p.z;}};struct _3DCH {struct fac {int a, b, c;bool ok;};int n;pt P[MAXV];int cnt;fac F[MAXV*8];int to[MAXV][MAXV];double vlen(pt a) {return sqrt(a.x * a.x + a.y * a.y + a.z * a.z);}double area(pt a, pt b, pt c) {return vlen((b - a) * (c - a));}double volume(pt a, pt b, pt c, pt d) {return (b - a) * (c - a) ^ (d - a);} // 四面体有向体积*6double ptof(pt &p, fac &f) {pt m = P[f.b] - P[f.a], n = P[f.c] - P[f.a], t = p - P[f.a];return (m * n) ^ t;}void deal(int p, int a, int b) {int f = to[a][b];fac add;if (F[f].ok) {if (ptof(P[p], F[f]) > eps)dfs(p, f);else {add.a = b, add.b = a, add.c = p, add.ok = 1;to[p][b] = to[a][p] = to[b][a] = cnt;F[cnt++] = add;}}}void dfs(int p, int cur) {F[cur].ok = 0;deal(p, F[cur].b, F[cur].a);deal(p, F[cur].c, F[cur].b);deal(p, F[cur].a, F[cur].c);}bool same(int s, int t) {pt &a = P[F[s].a], &b = P[F[s].b], &c = P[F[s].c];return fabs(volume(a, b, c, P[F[t].a])) < eps && fabs(volume(a, b, c,P[F[t].b])) < eps && fabs(volume(a, b, c, P[F[t].c])) < eps;}void construct() {int i;cnt = 0;if (n < 4)return;bool sb = 1;for (i = 1; i < n; i++) {if (vlen(P[0] - P[i]) > eps) {swap(P[1], P[i]);sb = 0;break;}}if (sb)return;sb = 1;for (i = 2; i < n; i++) {if (vlen((P[0] - P[1]) * (P[1] - P[i])) > eps) {swap(P[2], P[i]);sb = 0;break;}}if (sb)return;sb = 1;for (i = 3; i < n; i++) {if (fabs((P[0] - P[1]) * (P[1] - P[2]) ^ (P[0] - P[i])) > eps) {swap(P[3], P[i]);sb = 0;break;}}if (sb)return;fac add;for (i = 0; i < 4; i++) {add.a = (i + 1) % 4, add.b = (i + 2) % 4, add.c = (i + 3) % 4, add.ok= 1;if (ptof(P[i], add) > 0)swap(add.b, add.c);to[add.a][add.b] = to[add.b][add.c] = to[add.c][add.a] = cnt;F[cnt++] = add;}for (i = 4; i < n; i++) {for (int j = 0; j < cnt; j++) {if (F[j].ok && ptof(P[i], F[j]) > eps) {dfs(i, j);break;}}}int tmp = cnt;cnt = 0;for (i = 0; i < tmp; i++) {if (F[i].ok) {F[cnt++] = F[i];}}}double area() {double ret = 0.0;for (int i = 0; i < cnt; i++) {ret += area(P[F[i].a], P[F[i].b], P[F[i].c]);}return ret / 2.0;}double volume() {pt O(0, 0, 0);double ret = 0.0;for (int i = 0; i < cnt; i++) {ret += volume(O, P[F[i].a], P[F[i].b], P[F[i].c]);}return fabs(ret / 6.0);}int facetCnt_tri() {return cnt;}int facetCnt() {int ans = 0;for (int i = 0; i < cnt; i++) {bool nb = 1;for (int j = 0; j < i; j++) {if (same(i, j)) {nb = 0;break;}}ans += nb;}return ans;}};_3DCH hull;int main() {while (~scanf("%d", &hull.n)) {for (int i = 0; i < hull.n; i++)scanf("%lf%lf%lf", &hull.P[i].x, &hull.P[i].y, &hull.P[i].z);hull.construct();printf("%d\n", hull.facetCnt());}return 0;}