Submission #1007179

#	Time	Username	Problem	Language	Result	Execution time	Memory
1007179		BuzzyBeez	Joker (BOI20_joker)	C++17	100 / 100	202 ms	26308 KiB

Joker

#pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second

pair<int, int> E[200008];
int best[200008];

struct Disjoint_Set_Union {
	static const int N = 2e5;
	int par[N + 8], dis[N + 8], sz[N + 8];
	vector<pair<int*, int>> history; int is_bi = 1;
	Disjoint_Set_Union() {
		iota(par, par + N + 8, 0);
		fill(dis, dis + N + 8, 0);
		fill(sz, sz + N + 8, 1);
	}
	pair<int, int> pu, pv; int du, dv;
	pair<int, int> find(int u) {
		du = 0;
		while (par[u] != u) du ^= dis[u], u = par[u];
		return {u, du};
	}
	void join(int u, int v) {
		pu = find(u); pv = find(v);
		u = pu.first; du = pu.second; v = pv.first; dv = pv.second;
		if (u == v) {
			if (du == dv) history.push_back({&is_bi, is_bi}), is_bi = 0;
			return;
		}
		if (sz[u] < sz[v]) swap(u, v);
		history.push_back({par + v, par[v]});
		history.push_back({dis + v, dis[v]});
		history.push_back({sz + u, sz[u]});
		par[v] = u; dis[v] = du ^ dv ^ 1; sz[u] += sz[v];
	}
	int current_snapshot() {return history.size();}
	void rollback_to(int snapshot) {
		while (history.size() > snapshot) {
			*history.back().first = history.back().second;
			history.pop_back();
		}
	}
} DSU;

void dnc(int l, int r, int optl, int optr) {
	if (l > r) return;
	int mid = (l + r) / 2, cur = DSU.current_snapshot();
	for (int i = l; i < mid; ++i) DSU.join(E[i].fi, E[i].se);
	int post_L = DSU.current_snapshot();
	for (int i = optr; i >= max(mid, optl); --i) {
		if (!DSU.is_bi) {best[mid] = i; break;}
		DSU.join(E[i].fi, E[i].se);
	}
	if (!best[mid]) best[mid] = mid - 1;
	DSU.rollback_to(post_L); DSU.join(E[mid].fi, E[mid].se);
	dnc(mid + 1, r, best[mid], optr);
	DSU.rollback_to(cur);
	for (int i = optr; i > best[mid]; --i) DSU.join(E[i].fi, E[i].se);
	dnc(l, mid - 1, optl, best[mid]);
	DSU.rollback_to(cur);
}

signed main() {
	// freopen("NOHOME.INP", "r", stdin);
	// freopen("NOHOME.OUT", "w", stdout);
	ios_base::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	int n, m, q, l, r; cin >> n >> m >> q;
	for (int i = 1; i <= m; ++i) cin >> E[i].first >> E[i].second;
	dnc(1, m, 1, m);
	// for (int i = 1; i <= m; ++i) cout << best[i] << ' ';
	// cout << '\n';
	while (q--) cin >> l >> r, cout << (best[l] >= r ? "YES\n" : "NO\n");
}

Compilation message (stderr)

Joker.cpp: In member function 'void Disjoint_Set_Union::rollback_to(int)':
Joker.cpp:40:25: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int*, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   40 |   while (history.size() > snapshot) {
      |          ~~~~~~~~~~~~~~~^~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 8 / 8
• Subtask 3: 25 / 25
• Subtask 4: 10 / 10
• Subtask 5: 22 / 22
• Subtask 6: 29 / 29