#include <bits/stdc++.h>
using namespace std;
/*
void build(vector<int> a, vector<int> b, vector<int> c, vector<int> d) {
for (int i=0; i<a.size(); i++) {
cout << a[i] << " " << b[i] << " " << c[i] << " " << d[i] << "\n";
}
return;
}
*/
const int c=200005;
int ki[c], n, cnt;
map<pair<int, int>, int> m;
set<pair<int, int> > s;
vector<int> ans[4];
int ert(int a, int b) {
if (m.find({a, b})!=m.end()) {
return m[{a, b}];
}
return 0;
}
int holvan(int a) {
return (ki[a] ? ki[a]=holvan(ki[a]) : a);
}
void unio(int a, int b) {
a=holvan(a), b=holvan(b);
if (a!=b) {
ki[a]=b;
cnt++;
}
}
void add(int a, int b, pair<int, int> c) {
unio(a, b);
ans[0].push_back(a-1), ans[1].push_back(b-1), ans[2].push_back(c.first), ans[3].push_back(c.second);
}
int construct_roads(vector<int> a, vector<int> b) {
n=a.size();
for (int i=0; i<n; i++) {
int x=a[i], y=b[i];
m[{x, y}]=i+1;
s.insert({x-1, y-1}), s.insert({x-1, y+1}), s.insert({x+1, y-1}), s.insert({x+1, y+1});
}
for (auto p:s) {
int x=p.first, y=p.second;
int a=ert(x-1, y-1), b=ert(x-1, y+1), c=ert(x+1, y-1), d=ert(x+1, y+1), aa=0, bb=0;
/*cout << x << " " << y << " " << a << " " << b << " " << c << " " << d << "\n";
if (x==-1 && y==1) {
cout << "fontos " << x+1 << " " << y+1 << " " << ert(x+1, y+1) << "\n";
}*/
bool s=(x+y)%4;
if (s && !aa && a && b) aa=a, bb=b;
if (s && !aa && c && d) aa=c, bb=d;
if (!s && !aa && a && c) aa=a, bb=c;
if (!s && !aa && b && d) aa=b, bb=d;
if (aa) {
add(aa, bb, p);
}
}
if (cnt==n-1) {
build(ans[0], ans[1], ans[2], ans[3]);
}
return (cnt==n-1);
}
/*
int main()
{
int n;
vector<int> a, b;
cin >> n;
for (int i=1; i<=n; i++) {
int x, y;
cin >> x >> y;
a.push_back(x), b.push_back(y);
}
int x=construct_roads(a, b);
cout << x << "\n";
return 0;
}
*/
/*
2
0 0
0 2
*/
Compilation message
parks.cpp: In function 'int construct_roads(std::vector<int>, std::vector<int>)':
parks.cpp:66:9: error: 'build' was not declared in this scope
66 | build(ans[0], ans[1], ans[2], ans[3]);
| ^~~~~
