题解

依旧代码：

#include <bits/stdc++.h>
#define N 100005
#define x first
#define y second
using namespace std;
typedef pair<double,double> point;
const double eps=1e-8;
const double pi=acos(-1);

int e[N],ne[N],h[N],w[N],idx;
int vis[1005],dis[1005];
int ed[1005];
typedef pair<int,int> pii;
const int inf=0x3f3f3f3f;

void add(int u,int v,int dist) {
	e[idx]=v,ne[idx]=h[u],w[idx]=dist,h[u]=idx++;
}

point p[N];
int cnt;
int q[N],hh,tt;

struct line {
	point x,y;
	int id;
} l[N];

int sign(double x) {
	if(fabs(x)<eps) return 0;
	return x<0?-1:1;
}

int fcmp(double x,double y) {
	if(fabs(x-y)<eps) return 0;
	return x<y?-1:1;
}

point operator+(const point& a,const point& b) {
	return {a.x+b.x,a.y+b.y};
}

point operator-(const point& a,const point& b) {
	return {a.x-b.x,a.y-b.y};
}

point operator*(const point& a,double b) {
	return {a.x*b,a.y*b};
}

point operator/(const point& a,double b) {
	return {a.x/b,a.y/b};
}

double dot(const point& a,const point& b) {
	return a.x*b.x+a.y*b.y;
}

double cross(const point& a,const point& b) {
	return a.x*b.y-a.y*b.x;
}

double area(const point& a,const point& b,const point& c) {
	return cross(b-a,c-a);
}

double len(const point& a) {
	return sqrt(dot(a,a));
}

double get_dist(const point& a,const point& b) {
	return len(a-b);
}

double get_angle(const line& a) {
	point o=a.y-a.x;
	return atan2(o.y,o.x);
}

bool cmp(const line& a,const line& b) {
	double angle1=get_angle(a),angle2=get_angle(b);
	if(!fcmp(angle1,angle2)) return area(a.x,a.y,b.y)>0;
	return angle1<angle2;
}

point rotate(const point& a,double b) {
	return {a.x*cos(b)+a.y*sin(b),-a.x*sin(b)+a.y*cos(b)};
}

point get_line_intersection(const point& p,const point& q,const point& v,const point& w) {
	point u=p-q;
	double t=cross(w,u)/cross(v,w);
	return p+v*t;
}

point get_line_intersection(const line& a,const line& b) {
	return get_line_intersection(a.x,b.x,a.y-a.x,b.y-b.x);
}

bool on_right(const line& a,const line& b,const line& c) {
	point o=get_line_intersection(b,c);
	return sign(area(a.x,a.y,o))<0;
}

void half_plane_intersection(int id) {
	hh=0,tt=-1;
	sort(l,l+cnt,cmp);
	for(int i=0; i<cnt; i++) {
		if(i&&!fcmp(get_angle(l[i]),get_angle(l[i-1]))) continue;
		while(hh+1<=tt&&!on_right(l[i],l[q[tt-1]],l[q[tt]])) tt--;
		while(hh+1<=tt&&!on_right(l[i],l[q[hh]],l[q[hh+1]])) hh++;
		q[++tt]=i;
	}
	while(hh+1<=tt&&!on_right(l[q[hh]],l[q[tt-1]],l[q[tt]])) tt--;
	while(hh+1<=tt&&!on_right(l[q[tt]],l[q[hh]],l[q[hh+1]])) hh++;
	for(int i=hh; i<=tt; i++) {
		int tmp=l[q[i]].id;
		if(tmp==-1) ed[id]=1;
		else add(id,tmp,1);
	}
}

line getmidline(const point& a,const point& b,int id) {
	point u=(a+b)/2;
	point v=b-a;
	return {u,u+rotate(v,pi/2),id};
}

void dij(int st) {
	priority_queue<pii,vector<pii>,greater<pii>> qq;
	memset(dis,0x3f,sizeof dis);
	dis[st]=1;
	qq.push({1,st});
	while(!qq.empty()) {
		auto p=qq.top();
		qq.pop();
		int u=p.y;
		if(vis[u]) continue;
		vis[u]=1;
		for(int i=h[u]; ~i; i=ne[i]) {
			int v=e[i];
			if(dis[u]+w[i]<dis[v]) {
				dis[v]=dis[u]+w[i];
				if(!vis[v]) qq.push({dis[v],v});
			}
		}
	}
}

int main() {
	int t;
	cin >> t;
	while(t--) {
		memset(h,-1,sizeof h);
		memset(ed,0,sizeof ed);
		memset(vis,0,sizeof vis);
		idx=0;
		int n;
		cin >> n;
		int a,b,c,d;
		double mindist=1e18;
		cin >> a >> b >> c >> d;
		point o= {c,d};
		int st;
		if(n==0) {
			cout << 0 << endl;
			continue;
		}
		int tot=0;
		for(int i=0; i<n; i++) {
			int xx,yy;
			cin >> xx >> yy;
			if(xx>a||yy>b||xx<0||yy<0) continue;
			p[tot]= {xx,yy};
			if(mindist>get_dist(p[tot],o)) {
				st=tot;
				mindist=get_dist(p[tot],o);
			}
			tot++;
		}
		for(int i=0; i<tot; i++) {
			cnt=0;
			for(int j=0; j<tot; j++) {
				if(j==i) continue;
				l[cnt++]=getmidline(p[i],p[j],j);
			}
			l[cnt++]= {{0,0},{0,b},-1};
			l[cnt++]= {{a,0},{0,0},-1};
			l[cnt++]= {{0,b},{a,b},-1};
			l[cnt++]= {{a,b},{a,0},-1};
			half_plane_intersection(i);
		}
		dij(st);
		int ans=0x3f3f3f3f;
		for(int i=0; i<tot; i++) if(ed[i]) ans=min(ans,dis[i]);
		cout << ans << endl;
	}
	return 0;
}

写吧！