Submission #1308825

#	Time	Username	Problem	Language	Result	Execution time	Memory
1308825		Nonoze	Flood (IOI07_flood)	C++20	100 / 100	283 ms	22720 KiB

flood

/*
*	Author: Nonoze
*	Created: Tuesday 06/01/2026
*/
#include <bits/stdc++.h>
using namespace std;

#ifndef DEBUG
	#define dbg(...)
#endif

// #define cout cerr << "OUT: "
#define endl '\n'
#define endlfl '\n' << flush
#define quit(x) return (void)(cout << x << endl)

template<typename T> void read(T& x) { cin >> x; }
template<typename T1, typename T2> void read(pair<T1, T2>& p) { read(p.first), read(p.second); }
template<typename T> void read(vector<T>& v) { for (auto& x : v) read(x); }
template<typename T1, typename T2> void read(T1& x, T2& y) { read(x), read(y); }
template<typename T1, typename T2, typename T3> void read(T1& x, T2& y, T3& z) { read(x), read(y), read(z); }
template<typename T1, typename T2, typename T3, typename T4> void read(T1& x, T2& y, T3& z, T4& zz) { read(x), read(y), read(z), read(zz); }
template<typename T> void print(vector<T>& v) { for (auto& x : v) cout << x << ' '; cout << endl; }

#define sz(x) (int)(x.size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define make_unique(v) sort(all(v)), v.erase(unique(all(v)), (v).end())
#define pb push_back
#define mp(a, b) make_pair(a, b)
#define fi first
#define se second
#define cmin(a, b) a = min(a, b)
#define cmax(a, b) a = max(a, b)
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
#define QYES quit("YES")
#define QNO quit("NO")

#define int long long
#define double long double
const int inf = numeric_limits<int>::max() / 4;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD = 1e9+7, LOG=20;



void solve();

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	int tt=1;
	// cin >> tt;
	while(tt--) solve();
	return 0;
}



struct point {
	int x, y;
	vector<pair<int, int>> adj;
};


int n, k, m, q;
vector<point> a;
vector<int> idx, par;
vector<bool> visited, type;
vector<pair<int, int>> edges;
set<pair<int, int>> added;
set<int> edge_used;
vector<int> ans;

void dfs(int edge, bool sense) {
	if (visited[edge*2+sense]) return;
	visited[edge*2+sense]=1;
	auto [u, v] = edges[edge];
	if (!sense) swap(u, v);
	dbg(u, v);
	added.insert({u, v});
	if (!added.count({v, u})) edge_used.insert(edge);
	else ans.pb(edge);
	for (int i=0; i<sz(a[v].adj); i++) {
		if (a[v].adj[i].fi==u) {
			i++; i%=sz(a[v].adj);
			while (visited[a[v].adj[i].se*2 + (edges[a[v].adj[i].se].fi==v)]) {
				if (added.count({v, a[v].adj[i].fi})) return;
				i++; i%=sz(a[v].adj);
			}
			auto [to, eid] = a[v].adj[i];
			return dfs(eid, edges[eid].fi==v);
		}
	}
}



void solve() {
	read(n);
	map<int, int> compressx, compressy;
	a.clear(), a.resize(n); for (auto &u: a) read(u.x, u.y), compressx[u.x], compressy[u.y];
	{
		int cnt=0;
		for (auto &p : compressx) p.se=cnt++;
		cnt=0;
		for (auto &p : compressy) p.se=cnt++;
		for (auto &u: a) {
			u.x=compressx[u.x];
			u.y=compressy[u.y];
			// cout << u.x << ' ' << u.y << endl;
		}
	}
	read(m);
	vector<int> up(m);
	for (int t=0; t<m; t++) {
		int i, j; read(i, j); i--, j--;
		a[i].adj.pb({j, t});
		a[j].adj.pb({i, t});
		edges.pb({i, j});
		if (a[i].y<a[j].y) up[t]=2*t+1;
		else up[t]=2*t;
	}
	for (int i=0; i<n; i++) {
		sort(all(a[i].adj), [&](pair<int,int> u, pair<int,int> v) {
			int dx1=a[u.fi].x - a[i].x, dy1=a[u.fi].y - a[i].y;
			int dx2=a[v.fi].x - a[i].x, dy2=a[v.fi].y - a[i].y;
			return atan2l(dy1, dx1) > atan2l(dy2, dx2);
		});
	}

	vector<int> edges_sorted(m); iota(all(edges_sorted), 0);
	sort(all(edges_sorted), [&](int u, int v) {
		auto [u1, v1] = edges[u];
		auto [u2, v2] = edges[v];
		int mnx1=min(a[u1].x, a[v1].x), mnx2=min(a[u2].x, a[v2].x);
		if (mnx1!=mnx2) return mnx1 < mnx2;
		int mny1=min(a[u1].y, a[v1].y), mny2=min(a[u2].y, a[v2].y);
		return mny1 < mny2;
	});
	
	visited.resize(m*2+2, 0);
	vector<vector<pair<int, int>>> blocks;
	map<pair<int, int>, int> edge_to_block;
	for (auto eid: edges_sorted) if (!visited[up[eid]] && (a[edges[eid].fi].x==a[edges[eid].se].x)) {
		auto [u, v] = edges[eid];
		int sense=up[eid]&1;
		added.clear(), edge_used.clear();
		dfs(eid, sense);
		for (auto &x: edge_used) visited[x*2]=visited[x*2+1]=1;
		dbg(ans);
	}
	for (int i=0; i<m; i++) if (!visited[i*2]) ans.pb(i);
	sort(all(ans));
	cout << sz(ans) << endl;
	for (auto x: ans) cout << x+1 << endl;
}

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 3 / 3
• Subtask 5: 10 / 10
• Subtask 6: 3 / 3
• Subtask 7: 3 / 3
• Subtask 8: 3 / 3
• Subtask 9: 3 / 3
• Subtask 10: 9 / 9
• Subtask 11: 9 / 9
• Subtask 12: 9 / 9
• Subtask 13: 9 / 9
• Subtask 14: 9 / 9