#include<bits/stdc++.h> //#include "minesweeper.h" typedef int ll; #define fi first #define se second #define pii pair<ll,ll> #define N 1000006 #define endl '\n' using namespace std; const ll inf = 1e9; bool ghuy4g; ll n, m; pii a[N]; ll side[N][4][2], d[N], xof[N]; set<pii> s; vector<ll> adj[N]; void pre() { cin >> m; for (int i = 1; i <= m; i ++) { ll u, v; cin >> u >> v; if (a[u].fi == a[v].fi) { // doc if (a[u].se > a[v].se) swap(u, v); side[u][1][0] = i; // 0: di ra // 1: di vao side[u][1][1] = i + m; side[v][3][0] = i + m; side[v][3][1] = i; xof[i] = a[u].fi; } else { // ngang if (a[u].fi > a[v].fi) swap(u, v); side[u][0][0] = i; side[u][0][1] = i + m; side[v][2][0] = i + m; side[v][2][1] = i; xof[i] = inf; } s.insert({xof[i], i}); } for (int i = 1; i <= n; i ++) { for (int j = 0; j < 4; j ++) { if (side[i][j][1]) { ll jj = j; if (j == 1) jj = 3; if (j == 3) jj = 1; if (j == 2) jj = 0; if (j == 0) jj = 2; for (int k = (jj - 1 + 4) % 4;; k = (k + 1) % 4) { if (side[i][k][0]) { ll x = side[i][j][1]; ll y = side[i][k][0]; adj[x].push_back(y); adj[y].push_back(x); //cout << "i: " << i << " " << j << " " << k << endl; //cout << " x y: " << x << " " << y << endl; break; } } } } } for (int i = 1; i <= m + m; i ++) { d[i] = inf; } while (s.size()) { pii xet = *s.begin(); s.erase(xet); deque<pii> dq; xet.se = xet.se + m; d[xet.se] = 0; dq.push_front({d[xet.se], xet.se}); while (dq.size()) { ll u = dq.front().se, c = dq.front().fi; dq.pop_front(); //cout << " c u " << c << " " << u << endl; if (u <= m) { if (s.find({xof[u], u}) != s.end()) { s.erase({xof[u], u}); } } if (c > d[u]) continue; for (auto v : adj[u]) { if (d[v] > d[u]) { d[v] = d[u]; dq.push_front({d[v], v}); } } ll nguoc; if (u <= m) nguoc = u + m; else nguoc = u - m; if (d[nguoc] > d[u] + 1) { d[nguoc] = d[u] + 1; dq.push_back({d[nguoc], nguoc}); } } } vector<ll> res; for (int i = 1; i <= m; i ++) { if (d[i] == d[i + m]) { res.push_back(i); //cout << "i " << i << " " << d[i] << endl; } } cout << res.size() << endl; for (auto it : res) { cout << it << endl; } } bool klinh; signed main() { if (fopen("kghmdlod.inp", "r")) { freopen("kghmdlod.inp", "r", stdin); freopen("kghmdlod.out", "w", stdout); } srand(time(0)); ios_base::sync_with_stdio(0); cin.tie(0); cin >> n; for (int i = 1; i <= n; i ++) { cin >> a[i].fi >> a[i].se; } pre(); cerr << fabs(&klinh - &ghuy4g) / double(1024 * 1024); }

flood.cpp: In function 'int main()':
flood.cpp:120:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  120 |                 freopen("kghmdlod.inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
flood.cpp:121:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  121 |                 freopen("kghmdlod.out", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~