Language: C++

#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i=0; i < (n); i++)
typedef double D;
typedef complex<D> P;
typedef pair<P, P> L;
typedef vector<P> VP;
typedef vector<VP> Vcon;
const D EPS = 1e-7; 
#define X real()
#define Y imag()
#define LE(n,m) ((n) < (m) + EPS)
#define GE(n,m) ((n) + EPS > (m))
#define EQ(n,m) (abs((n)-(m)) < EPS)
D dot(P a, P b) {return (conj(a)*b).X; }
D cross(P a, P b) {  return (conj(a)*b).Y;}
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 isparallel(L a,L b){
  return cross(a.first-a.second,b.first-b.second) == 0.0 ;
}

bool isecLP(P a1, P a2, P b) {
  return abs(ccw(a1, a2, b)) != 1;  
}

bool isecLL(P a1, P a2, P b1, P b2) {
  return !isecLP(a2-a1, b2-b1, 0) || isecLP(a1, b1, b2);
}

bool isecLS(P a1, P a2, P b1, P b2) {
  return cross(a2-a1, b1-a1) * cross(a2-a1, b2-a1) < EPS;
}

bool isecSS(P a1, P a2, P b1, P b2) {
  return ccw(a1, a2, b1)*ccw(a1, a2, b2) <= 0 &&
         ccw(b1, b2, a1)*ccw(b1, b2, a2) <= 0;
}
 
// 線分と点
bool isecSP(P a1, P a2, P b) {
  return !ccw(a1, a2, b);
  //return abs(a1 - b) + abs(a2 - b) - abs(a2 - a1) < EPS;  //Perfective
}
 

P crosspointLL(P a1, P a2, P b1, P b2) {
  D d1 = cross(b2-b1, b1-a1);
  D d2 = cross(b2-b1, a2-a1);
  if (EQ(d1, 0) && EQ(d2, 0)) return a1;  // same line
  if (EQ(d2, 0)) throw "kouten ga nai";   // 交点がない
  return a1 + d1/d2 * (a2-a1);
}
namespace std {
  bool operator<(const P a, const P b) {
    return a.X != b.X ? a.X < b.X : a.Y < b.Y;
  }
}

VP convexHull(VP ps) {  
  int n = ps.size(), k = 0;
  sort(ps.begin(), ps.end());
  VP ch(2*n);
  for (int i = 0; i < n; ch[k++] = ps[i++]);
    while (k >= 2 && ccw(ch[k-2], ch[k-1], ps[i]) <= 0) --k;  
  for (int i = n-2, t = k+1; i >= 0; ch[k++] = ps[i--]) 
    while (k >= t && ccw(ch[k-2], ch[k-1], ps[i]) <= 0) --k;
  ch.resize(k-1);
  return ch;
}

bool isCcwConvex(const VP& ps) {
  int n = ps.size();
  rep (i, n) if (ccw(ps[i], ps[(i+1) % n], ps[(i+2) % n]) == -1) return false;
  return true;
}

int inConvex(P p, const VP& ps) {
  int n = ps.size();
  int dir = ccw(ps[0], ps[1], p);
  rep (i, n) {
    int ccwc = ccw(ps[i], ps[(i + 1) % n], p);
    if (!ccwc) return 2;  // 線分上に存在
    if (ccwc != dir) return 0;
  }
  return 1;
}

int inPolygon(const VP& ps, P p) {
  int n = ps.size();
  bool in = false;
  rep (i, n) {
    P a = ps[i] - p;
    P b = ps[(i + 1) % n] - p;
    if (EQ(cross(a,b), 0) && LE(dot(a,b), 0)) return 2;
    if (a.Y > b.Y) swap(a,b);
    if ((a.Y*b.Y < 0 || (a.Y*b.Y < EPS && b.Y > EPS)) && LE(cross(a, b), 0)) in = !in;
  }
  return in;
}
 

VP convexCut(const VP& ps, P a1, P a2) {
  int n = ps.size();
  VP ret;
  rep(i,n) {
    int ccwc = ccw(a1, a2, ps[i]);
    if (ccwc != -1) ret.push_back(ps[i]);
    int ccwn = ccw(a1, a2, ps[(i + 1) % n]);
    if (ccwc * ccwn == -1) ret.push_back(crosspointLL(a1, a2, ps[i], ps[(i + 1) % n]));
  }
  return ret;
}
D area(const VP&);
bool isec_CS(const VP& ps, P a1, P a2){
  rep(i,ps.size()){
    if(isecLS(ps[i],ps[(i+1)%ps.size()],a1,a2))return true;
  }
  return false;
}

void divide_convex(VP ps,const VP &s1,const VP &s2,Vcon &V){
  bool flag = false;
  for(int i=0;i<s1.size();i++){
    VP convex_1=convexCut(ps,s1[i],s2[i]);
    VP convex_2=convexCut(ps,s2[i],s1[i]);
    if(area(convex_1)<EPS||area(convex_2)<EPS)continue;
    divide_convex(convex_1,s1,s2,V);
    divide_convex(convex_2,s1,s2,V);
    flag = true;
    break;
  }
  if(!flag) V.push_back(ps);
  return;
}


// 全く同じ辺を共有してれば１を返す。
bool isecCC(VP a1,VP a2){
  rep(i,a1.size()){
    rep(j,a2.size()){
      P e1=a1[i];
      P e2=a1[(i+1)%a1.size()];
      P e3=a2[j];
      P e4=a2[(j+1)%a2.size()];
      if(abs(e1-e3)<EPS&&abs(e2-e4)<EPS)return 1;
      if(abs(e1-e4)<EPS&&abs(e2-e3)<EPS)return 1;
    }
  }
  return 0;
}

// 頂点抜き
vector<vector<int> > Convex_arrangement(const Vcon& ps){
  int n=ps.size();
  vector<vector<int> >V(n,vector<int>(n));
  rep(i,n)rep(j,n)V[i][j]=1e8;
  rep(i,n){
    for(int j=i+1;j<n;j++){
      if(isecCC(ps[i],ps[j])){
        V[i][j]=1;
        V[j][i]=1;
      }
    }
  }
  return V;
}
 
// 多角形の符号付面積
D area(const VP& ps) {
  D a = 0;
  rep (i, ps.size()) a += cross(ps[i], ps[(i+1) % ps.size()]);
  return a / 2;
}

// 多角形a1が凸多角形a2を内包してるか
bool con_in_con(VP a1,VP a2){
  int p=0;
  rep(j,a2.size()){
    if(inPolygon(a1,a2[j])==0)return 0;
    if(inPolygon(a1,(a2[j]+a2[(j+1)%a2.size()])/2.0)==0)return 0;
  }
  return 1;
}

signed main(){
  vector<P>s1,s2;
  int n,m,q;
  cin>>n;
  VP V[n];
  rep(i,n){
    cin>>m;
    D x[m],y[m];
    rep(j,m){
      cin>>x[j]>>y[j];
      V[i].push_back(P(x[j],y[j]));
    }
    rep(j,m){
      s1.push_back(P(x[j],y[j]));
      s2.push_back(P(x[(j+1)%m],y[(j+1)%m]));
    }
  }
 
  VP convex;
  convex.push_back(P(-200000,-200000));
  convex.push_back(P(200000,-200000));
  convex.push_back(P(200000,200000));
  convex.push_back(P(-200000,200000));
  Vcon v;
 
  divide_convex(convex,s1,s2,v);
  vector<vector<int> > a=Convex_arrangement(v);
 
  int cnt[v.size()]={};
 
  rep(i,v.size()){
    rep(j,n){
      if(con_in_con(V[j],v[i])){
        cnt[i]++;
      }
    }
  }
  rep(i,v.size()){
    rep(j,v.size()){
      if(i==j)a[i][j]=0;
      if(a[i][j]==1){
        a[i][j]=abs(cnt[i]-cnt[j]);
      }
    }
  }
 
  rep(k,v.size())
    rep(i,v.size())
      rep(j,v.size())
        a[i][j]=min(a[i][j],a[i][k]+a[k][j]);
 
  cin>>q;
  while(q--){
    int A=1e9,B=1e9;
    D a1,a2,b1,b2;
    cin>>a1>>a2>>b1>>b2;
    rep(i,v.size()){
      if(inPolygon(v[i],P(a1,a2))){
        A=i;
        if(inPolygon(v[i],P(a1,a2))==1)break;
      }
    }
    rep(i,v.size()){
      if(inPolygon(v[i],P(b1,b2))){
        B=i;
        if(inPolygon(v[i],P(b1,b2))==1)break;
      }
    }
    cout<<a[A][B]<<endl;
  }
}



Compiler output:
a.cc: In function 'VP convexHull(VP)':
a.cc:71:47: error: 'i' was not declared in this scope
   71 |     while (k >= 2 && ccw(ch[k-2], ch[k-1], ps[i]) <= 0) --k;
      |                                               ^