Submission #1367861

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define all(c) (c).begin(),(c).end()
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define REP(i,m,n) for(int i=(int)(m);i<(int)(n);i++)
#define rep(i,n) REP(i,0,n)
#define iter(c) __typeof((c).begin())
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
#define pb(a) push_back(a)
#define rd(a) cin>>(a)
#define RD(a,b) cin>>(a)>>(b)
#define pr(a) cout<<(a)<<endl
#define PR(a,b) cout<<(a)<<" "<<(b)<<endl
#define F first
#define S second
#define ll long long
bool check(int n,int m,int x,int y){return (x<0||x>=n||y<0||y>=m)?false:true;}
const ll MAX=1000000007,MAXL=1LL<<60,dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};
typedef pair<double,int> P2;
const double EPS = 1e-10;
const double INF = 1e12;
typedef complex<double> P;
namespace std {
  bool operator < (const P& a, const P& b) {
    return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
  }
}
double cross(const P& a, const P& b) {
  return imag(conj(a)*b);
}
double dot(const P& a, const P& b) {
  return real(conj(a)*b);
}
struct L : public vector<P> {
  L(const P &a, const P &b) {
    push_back(a); push_back(b);
  }
};
 
double D(P a, P b) {
  return sqrt((a.real()-b.real())*(a.real()-b.real())+(a.imag()-b.imag())*(a.imag()-b.imag()));
}
 
int ccw(P a, P b, P c) {
  b -= a; c -= a;
  if (cross(b, c) > EPS)   return +1;
  if (cross(b, c) < -EPS)   return -1;
  if (dot(b, c) < -EPS)     return +2;
  if (norm(b) < norm(c)) return -2;
  return 0;
}
bool intersectSS(const L &s, const L &t) {
  return ccw(s[0],s[1],t[0])*ccw(s[0],s[1],t[1]) <= 0 &&
         ccw(t[0],t[1],s[0])*ccw(t[0],t[1],s[1]) <= 0;
}
 
P crosspoint(const L &l, const L &m) {
  double A = cross(l[1] - l[0], m[1] - m[0]);
  double B = cross(l[1] - l[0], l[1] - m[0]);
  if (fabs(A) < EPS && fabs(B) < EPS) return m[0];
  if (fabs(A) < EPS) assert(false);
  return m[0] + B / A * (m[1] - m[0]);
}
 
int main() {
  double x1,x2,y1,y2;
  RD(x1,y1);RD(x2,y2);
  P a1=P(x1,y1),a2=P(x2,y2);
  L l=L(a1,a2);
  int n;
  rd(n);
  vector<P> p;
  vector<P2> v;
  set<P> se;
  rep(i,n) {
    RD(x1,y1);
    P q=P(x1,y1);
    if(i) {
      L l2=L(p[p.size()-1],q);
      if(se.count(p[p.size()-1])) l2=L(p[p.size()-2],q);
      if(intersectSS(l,l2)) {
	P pp=crosspoint(l,l2);
	v.pb(P2(D(a1,pp),p.size()));
	p.pb(pp);
	se.insert(pp);
      }
    }
    p.pb(P(x1,y1));
  }
  L l2=L(p[0],p[p.size()-1]);
  if(intersectSS(l,l2)) {
    P pp=crosspoint(l,l2);
    v.pb(P2(D(a1,pp),p.size()));	
    p.pb(pp);
    se.insert(pp);
  }
  sort(all(v));
  bool used[p.size()];
  fill(used,used+p.size(),false);
  int ans=0;
  rep(i,p.size()) {
    if(se.count(p[i]) || used[i]) continue;
    ans++;
    int k=i;
    bool b[p.size()];
    fill(b,b+p.size(),false);
    bool ck=false;
    while(!b[k]) {
      used[k]=true;
      b[k]=true;
      if(se.count(p[k])) used[k]=false;
      if(se.count(p[k]) && !ck) {
	int t=0;
	rep(j,v.size()) {
	  if(v[j].S==k) {
	    t=j;
	    break;
	  }
	}
	if(t%2) k=v[t-1].S;
	else k=v[t+1].S;
	ck=true;
      } else {
	k=(k+1)%p.size();
	ck=false;
      }
    }
  }
  pr(ans);
  return 0;
}

Submission Info

Judge Result