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 310
struct 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*6
	double 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;
}