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190 | #include <algorithm>
#include <cmath>
#include <cstring>
#include <list>
#include <utility>
#include <vector>
const double EPS = 1e-8;
const int MAXV = 10000;
struct Point {
double x, y;
int id;
Point(double a = 0, double b = 0, int c = -1) : x(a), y(b), id(c) {}
bool operator<(const Point &a) const {
return x < a.x || (fabs(x - a.x) < EPS && y < a.y);
}
bool operator==(const Point &a) const {
return fabs(x - a.x) < EPS && fabs(y - a.y) < EPS;
}
double dist2(const Point &b) {
return (x - b.x) * (x - b.x) + (y - b.y) * (y - b.y);
}
};
struct Point3D {
double x, y, z;
Point3D(double a = 0, double b = 0, double c = 0) : x(a), y(b), z(c) {}
Point3D(const Point &p) { x = p.x, y = p.y, z = p.x * p.x + p.y * p.y; }
Point3D operator-(const Point3D &a) const {
return Point3D(x - a.x, y - a.y, z - a.z);
}
double dot(const Point3D &a) { return x * a.x + y * a.y + z * a.z; }
};
struct Edge {
int id;
std::list<Edge>::iterator c;
Edge(int id = 0) { this->id = id; }
};
int cmp(double v) { return fabs(v) > EPS ? (v > 0 ? 1 : -1) : 0; }
double cross(const Point &o, const Point &a, const Point &b) {
return (a.x - o.x) * (b.y - o.y) - (a.y - o.y) * (b.x - o.x);
}
Point3D cross(const Point3D &a, const Point3D &b) {
return Point3D(a.y * b.z - a.z * b.y, -a.x * b.z + a.z * b.x,
a.x * b.y - a.y * b.x);
}
int inCircle(const Point &a, Point b, Point c, const Point &p) {
if (cross(a, b, c) < 0) std::swap(b, c);
Point3D a3(a), b3(b), c3(c), p3(p);
b3 = b3 - a3, c3 = c3 - a3, p3 = p3 - a3;
Point3D f = cross(b3, c3);
return cmp(p3.dot(f)); // check same direction, in: < 0, on: = 0, out: > 0
}
int intersection(const Point &a, const Point &b, const Point &c,
const Point &d) { // seg(a, b) and seg(c, d)
return cmp(cross(a, c, b)) * cmp(cross(a, b, d)) > 0 &&
cmp(cross(c, a, d)) * cmp(cross(c, d, b)) > 0;
}
class Delaunay {
public:
std::list<Edge> head[MAXV]; // graph
Point p[MAXV];
int n, rename[MAXV];
void init(int n, Point p[]) {
memcpy(this->p, p, sizeof(Point) * n);
std::sort(this->p, this->p + n);
for (int i = 0; i < n; i++) rename[p[i].id] = i;
this->n = n;
divide(0, n - 1);
}
void addEdge(int u, int v) {
head[u].push_front(Edge(v));
head[v].push_front(Edge(u));
head[u].begin()->c = head[v].begin();
head[v].begin()->c = head[u].begin();
}
void divide(int l, int r) {
if (r - l <= 2) { // #point <= 3
for (int i = l; i <= r; i++)
for (int j = i + 1; j <= r; j++) addEdge(i, j);
return;
}
int mid = (l + r) / 2;
divide(l, mid);
divide(mid + 1, r);
std::list<Edge>::iterator it;
int nowl = l, nowr = r;
for (int update = 1; update;) {
// find left and right convex, lower common tangent
update = 0;
Point ptL = p[nowl], ptR = p[nowr];
for (it = head[nowl].begin(); it != head[nowl].end(); it++) {
Point t = p[it->id];
double v = cross(ptR, ptL, t);
if (cmp(v) > 0 || (cmp(v) == 0 && ptR.dist2(t) < ptR.dist2(ptL))) {
nowl = it->id, update = 1;
break;
}
}
if (update) continue;
for (it = head[nowr].begin(); it != head[nowr].end(); it++) {
Point t = p[it->id];
double v = cross(ptL, ptR, t);
if (cmp(v) < 0 || (cmp(v) == 0 && ptL.dist2(t) < ptL.dist2(ptR))) {
nowr = it->id, update = 1;
break;
}
}
}
addEdge(nowl, nowr); // add tangent
for (int update = 1; true;) {
update = 0;
Point ptL = p[nowl], ptR = p[nowr];
int ch = -1, side = 0;
for (it = head[nowl].begin(); it != head[nowl].end(); it++) {
if (cmp(cross(ptL, ptR, p[it->id])) > 0 &&
(ch == -1 || inCircle(ptL, ptR, p[ch], p[it->id]) < 0)) {
ch = it->id, side = -1;
}
}
for (it = head[nowr].begin(); it != head[nowr].end(); it++) {
if (cmp(cross(ptR, p[it->id], ptL)) > 0 &&
(ch == -1 || inCircle(ptL, ptR, p[ch], p[it->id]) < 0)) {
ch = it->id, side = 1;
}
}
if (ch == -1) break; // upper common tangent
if (side == -1) {
for (it = head[nowl].begin(); it != head[nowl].end();) {
if (intersection(ptL, p[it->id], ptR, p[ch])) {
head[it->id].erase(it->c);
head[nowl].erase(it++);
} else {
it++;
}
}
nowl = ch;
addEdge(nowl, nowr);
} else {
for (it = head[nowr].begin(); it != head[nowr].end();) {
if (intersection(ptR, p[it->id], ptL, p[ch])) {
head[it->id].erase(it->c);
head[nowr].erase(it++);
} else {
it++;
}
}
nowr = ch;
addEdge(nowl, nowr);
}
}
}
std::vector<std::pair<int, int> > getEdge() {
std::vector<std::pair<int, int> > ret;
ret.reserve(n);
std::list<Edge>::iterator it;
for (int i = 0; i < n; i++) {
for (it = head[i].begin(); it != head[i].end(); it++) {
if (it->id < i) continue;
ret.push_back(std::make_pair(p[i].id, p[it->id].id));
}
}
return ret;
}
};
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