3180000_re.cc

北大大牛代码 1240道题的原代码 超级权威

#include <iostream>
#include <cmath>
#include <algorithm>

using namespace std;

#define Oi(e) ((e)->oi)
#define Dt(e) ((e)->dt)
#define On(e) ((e)->on)
#define Op(e) ((e)->op)
#define Dn(e) ((e)->dn)
#define Dp(e) ((e)->dp)
#define Other(e, p) ((e)->oi == p ? (e)->dt : (e)->oi)
#define Next(e, p) ((e)->oi == p ? (e)->on : (e)->dn)
#define Prev(e, p) ((e)->oi == p ? (e)->op : (e)->dp)
#define V(p1, p2, u, v) (u = p2->x - p1->x, v = p2->y - p1->y)
#define C2(u1, v1, u2, v2) (u1 * v2 - v1 * u2)
#define C3(p1, p2, p3) ((p2->x - p1->x) * (p3->y - p1->y) - (p2->y - p1->y) * (p3->x - p1->x))
#define Dot(u1, v1, u2, v2) (u1 * u2 + v1 * v2)

#define MAXN 1000001

struct point {
	double x, y;
	struct edge *in;
	bool operator < (const point &p1) const {
		return x < p1.x || (x == p1.x && y < p1.y);
	}
};

struct edge {
	point *oi, *dt;
	edge *on, *op, *dn, *dp;
};

struct gEdge {
	int u, v;
	double w;
	bool operator < (const gEdge &e1) const {return w < e1.w;}
}E[3 * MAXN], MST[MAXN];

int N, M, KK;
int f[MAXN], d[MAXN];

void Init() {
	for(int i = 0; i < N; ++i) f[i] = i, d[i] = 0;
}

int Find(int x) {
	int i = x, t = x;
	while(f[i] != i) i = f[i];
	while(f[t] != i) {
		int temp = f[t]; f[t] = i; t = temp;
	}
	return i;
}

void Make(int x, int y) {
	x = Find(x); y = Find(y);
	if(d[x] > d[y]) f[y] = x;
	else {
		f[x] = y;
		if(d[x] == d[y]) d[y]++;
	}
}

void Kruskal() 
{
	Init();
	sort(E, E + M);
	for(int i = 0, k = 0; i < M && k < N - 1; ++i) {
		if(Find(E[i].u) != Find(E[i].v)) {
			KK--;
			Make(E[i].u, E[i].v); MST[k++] = E[i]; 
			if(KK==0)
			{
				printf("%d\n",int(ceil(E[i].w)));
				return ;
			}
		}
	}
}

point p[MAXN], *Q[MAXN];
edge mem[3 * MAXN], *elist[3 * MAXN];
int nfree;

void Alloc_memory() {
	nfree = 3 * N;
	edge *e = mem;
	for(int i = 0; i < nfree; ++i) elist[i] = e++;
}

void Splice(edge *a, edge *b, point *v) {
	edge *next;
	if(Oi(a) == v) next = On(a), On(a) = b;
	else next = Dn(a), Dn(a) = b;
	if(Oi(next) == v) Op(next) = b;
	else Dp(next) = b;
	if(Oi(b) == v) On(b) = next, Op(b) = a;
	else Dn(b) = next, Dp(b) = a;
}

edge *Make_edge(point *u, point *v) {
	edge *e = elist[--nfree];
	e->on = e->op = e->dn = e->dp = e; e->oi = u; e->dt = v;
	if(u->in == NULL) u->in = e; if(v->in == NULL) v->in = e;
	return e;
}

edge *Join(edge *a, point *u, edge *b, point *v, int side) {
	edge *e = Make_edge(u, v);
	if(side == 1) {
		if(Oi(a) == u) Splice(Op(a), e, u);
		else Splice(Dp(a), e, u);
		Splice(b, e, v);
	}
	else {
		Splice(a, e, u);
		if(Oi(b) == v) Splice(Op(b), e, v);
		else Splice(Dp(b), e, v);
	}
	return e;
}

void Remove(edge *e) {
	point *u = Oi(e), *v = Dt(e);
	if(u->in == e) u->in = e->on; if(v->in == e) v->in = e->dn;
	if(Oi(e->on) == u) e->on->op = e->op;
	else e->on->dp = e->op;
	if(Oi(e->op) == u) e->op->on = e->on;
	else e->op->dn = e->on;
	if(Oi(e->dn) == v) e->dn->op = e->dp;
	else e->dn->dp = e->dp;
	if(Oi(e->dp) == v) e->dp->on = e->dn;
	else e->dp->dn = e->dn;
	elist[nfree++] = e;
}

void Make_Graph() {
	for(int i = 0; i < N; ++i) {
		point *u = &p[i];
		edge *start = u->in, *e = u->in;
		do {
			point *v = Other(e, u);
			if(u < v) {
				E[M].u = u - p, E[M].v = v - p;
				E[M++].w = hypot(u->x - v->x, u->y - v->y);
			}
			e = Next(e, u);
		} while(e != start);
	}
}

void Low_tangent(edge *e_l, point *o_l, edge *e_r, point *o_r, edge **l_low, point **OL, edge **r_low, point **OR) {
	point *d_l = Other(e_l, o_l), *d_r = Other(e_r, o_r);
	while(true) {
		if(C3(o_l, o_r, d_l) < 0.0) {
			e_l = Prev(e_l, d_l);
			o_l = d_l; d_l = Other(e_l, o_l);
		}
		else if(C3(o_l, o_r, d_r) < 0.0) {
			e_r = Next(e_r, d_r);
			o_r = d_r; d_r = Other(e_r, o_r);
		}
		else break;
	}
	*OL = o_l, *OR = o_r;
	*l_low = e_l, *r_low = e_r;
}

void Merge(edge *lr, point *s, edge *rl, point *u, edge **tangent) {
	double l1, l2, l3, l4, r1, r2, r3, r4, cot_L, cot_R, u1, v1, u2, v2, N1, cot_N, P1, cot_P;
	point *O, *D, *OR, *OL;
	edge *B, *L, *R;
	Low_tangent(lr, s, rl, u, &L, &OL, &R, &OR);
	*tangent = B = Join(L, OL, R, OR, 0);
	O = OL, D = OR;
	do {
		edge *El = Next(B, O), *Er = Prev(B, D), *next, *prev;
		point *l = Other(El, O), *r = Other(Er, D);
		V(l, O, l1, l2); V(l, D, l3, l4); V(r, O, r1, r2); V(r, D, r3, r4);
		double cl = C2(l1, l2, l3, l4), cr = C2(r1, r2, r3, r4);
		bool BL = cl > 0.0, BR = cr > 0.0;
		if(!BL && !BR) break;
		if(BL) {
			double dl = Dot(l1, l2, l3, l4);
			cot_L = dl / cl;
			do {
				next = Next(El, O);
				V(Other(next, O), O, u1, v1); V(Other(next, O), D, u2, v2);
				N1 = C2(u1, v1, u2, v2);
				if(!(N1 > 0.0)) break;
				cot_N = Dot(u1, v1, u2, v2) / N1;
				if(cot_N > cot_L) break;
				Remove(El);
				El = next;
				cot_L = cot_N;
			} while(true);
		}
		if(BR) {
			double dr = Dot(r1, r2, r3, r4);
			cot_R = dr / cr;
			do {
				prev = Prev(Er, D);
				V(Other(prev, D), O, u1, v1); V(Other(prev, D), D, u2, v2);
				P1 = C2(u1, v1, u2, v2);
				if(!(P1 > 0.0)) break;
				cot_P = Dot(u1, v1, u2, v2) / P1;
				if(cot_P > cot_R) break;
				Remove(Er);
				Er = prev;
				cot_R = cot_P;
			} while(true);
		}
		l = Other(El, O); r = Other(Er, D);
		if(!BL || (BL && BR && cot_R < cot_L)) { B = Join(B, O, Er, r, 0); D = r; }
		else { B = Join(El, l, B, D, 0); O = l; }
	} while(true);
}

void Divide(int s, int t, edge **L, edge **R) {
	edge *a, *b, *c, *ll, *lr, *rl, *rr, *tangent;
	int n = t - s + 1;
	if(n == 2) *L = *R = Make_edge(Q[s], Q[t]);
	else if(n == 3) {
		a = Make_edge(Q[s], Q[s + 1]), b = Make_edge(Q[s + 1], Q[t]);
		Splice(a, b, Q[s + 1]);
		double v = C3(Q[s], Q[s + 1], Q[t]);
		if(v > 0.0) {
			c = Join(a, Q[s], b, Q[t], 0);
			*L = a; *R = b;
		}
		else if(v < 0.0) {
			c = Join(a, Q[s], b, Q[t], 1);
			*L = c; *R = c;
		}
		else { *L = a; *R = b; }
	}
	else if(n > 3) {
		int split = (s + t) / 2;
		Divide(s, split, &ll, &lr); Divide(split + 1, t, &rl, &rr);
		Merge(lr, Q[split], rl, Q[split + 1], &tangent);
		if(Oi(tangent) == Q[s]) ll = tangent;
		if(Dt(tangent) == Q[t]) rr = tangent;
		*L = ll; *R = rr;
	}
}

double tmp[MAXN][2];
int tmpcnt;

int main() 
{
	int i, cas;

	scanf("%d",&cas);
	while(cas-- > 0) {
		scanf("%d",&KK);
		tmpcnt = 0;
		while(1)
		{
			scanf("%lf",&tmp[tmpcnt][0]);
			if(tmp[tmpcnt][0]==-1)
				break;
			else
			{
				scanf("%lf",&tmp[tmpcnt][1]);
			}
			tmpcnt++;
			if(tmpcnt >= MAXN)
				while(1)
					puts("I love Shengqi");
		}
		N = tmpcnt;
		KK = N-KK;
		Alloc_memory();
		for(i = 0; i < N; ++i) {
			p[i].x = tmp[i][0];
			p[i].y = tmp[i][1];
			p[i].in = NULL;
		}
		sort(p, p + N);
		for(i = 0; i < N; i++) Q[i] = p + i;
		edge *L, *R;
		Divide(0, N - 1, &L, &R);
		M = 0;
		Make_Graph();
		Kruskal();
	}
	return 0;
}