Submission #469254

#	Time	Username	Problem	Language	Result	Execution time	Memory
469254		islingr	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	77 ms	15424 KiB

oneway

#include <bits/stdc++.h>
using namespace std;

template<class T> bool uin(T& a, const T& b) { return a > b ? a = b, true : false; }

signed main() {
	cin.tie(nullptr)->sync_with_stdio(false);

	int n, m; cin >> n >> m;
	
	vector<vector<int>> g(n);
	vector<int> l(m), r(m), in(n), low(n), s(n);

	for (int e = 0; e < m; ++e) {
		cin >> l[e] >> r[e]; --l[e]; --r[e];
		g[l[e]].push_back(e);
		g[r[e]].push_back(e);	
	}

	int q; cin >> q;
	while (q--) {
		int u, v; cin >> u >> v; --u; --v;
		++s[u]; --s[v];
	}

	string ans(m, 'B');
	int timer = 0;
	constexpr char dir[2] = {'L', 'R'};
	
	auto dfs = [&](const auto &self, int u, int p) -> void {
		low[u] = in[u] = ++timer;
		for (auto e : g[u]) {
			if (e == p) continue;
			int v = l[e] ^ r[e] ^ u;
			if (in[v] != 0) uin(low[u], in[v]);
			else {
				self(self, v, e);
				uin(low[u], low[v]);
				if (s[v] != 0 && in[u] < low[v])
					ans[e] = dir[(l[e] != v) ^ (s[v] > 0)];
				s[u] += s[v];
			}
		}
	};
	
	for (int u = 0; u < n; ++u)
		if (in[u] == 0)
			dfs(dfs, u, -1);
	
	cout << ans << '\n';
}

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40