#include "parks.h"
#include <bits/stdc++.h>
using namespace std;
int construct_roads(vector<int> x, vector<int> y) {
int N = x.size();
map<pair<int,int>,int> mp;
for(int i = 0;i < N;i++) mp[{x[i],y[i]}] = i;
vector<int> vis(N,false);
int dx[4] = {0,2,-2,0};
int dy[4] = {2,0,0,-2};
vector<int> u,v,a,b;
set<pair<int,int>> banned;
function<bool(int,int)> add_road = [&](int aidx,int bidx){
int midx = (x[aidx]+x[bidx])/2;
int midy = (y[aidx]+y[bidx])/2;
if(x[aidx] == x[bidx]){
// vertical
if((midy/2)%2 == (midx/2)%2){
midx++;
}else{
midx--;
}
}else{
// horizontal
if((midx/2)%2 == (midy/2)%2){
midy--;
}else{
midy++;
}
}
if(banned.count({midx,midy})) return false;
banned.insert({midx,midy});
{
int nidx1 = -1,nidx2 = -1;
for(int d = 0;d < 4;d++){
int nx = midx+dx[d]/2;
int ny = midy+dy[d]/2;
if(nx == x[aidx] && ny == y[aidx]) continue;
if(nx == x[bidx] && ny == y[bidx]) continue;
if(mp.count({nx,ny})){
if(nidx1 == -1) nidx1 = mp[{nx,ny}];
else nidx2 = mp[{nx,ny}];
}
}
if(nidx1 != -1 && nidx2 != -1){
vis[nidx1] = true;
vis[nidx2] = true;
if(x[aidx] == x[nidx1] || y[aidx] == y[nidx1]){
add_road(aidx,nidx1);
add_road(bidx,nidx2);
}else{
add_road(aidx,nidx2);
add_road(bidx,nidx1);
}
}
}
u.push_back(aidx);
v.push_back(bidx);
a.push_back(midx);
b.push_back(midy);
return true;
};
function<void(int)> dfs = [&](int idx){
// cout << "!" << idx << endl;
vis[idx] = true;
int cx = x[idx],cy = y[idx];
for(int d = 0;d < 4;d++){
int nx = cx+dx[d];
int ny = cy+dy[d];
if(!mp.count({nx,ny})) continue;
int nidx = mp[{nx,ny}];
if(vis[nidx]) continue;
if(add_road(idx,nidx)) ;
dfs(nidx);
}
};
dfs(0);
for(int i = 1;i < N;i++){
if(vis[i]) dfs(i);// check if filled by square
}
for(auto &i:vis){
if(!i) return 0;
}
build(u,v,a,b);
return true;
}
