Submission #491129

#	Time	Username	Problem	Language	Result	Execution time	Memory
491129		hollwo_pelw	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	75 ms	16768 KiB

oneway

/*
// is short or still long ???
hollwo_pelw's template(short)
// Note : -Dhollwo_pelw_local
*/

#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/trie_policy.hpp>
// #include <ext/rope>

using namespace std;
// using namespace __gnu_pbds;
// using namespace __gnu_cxx;

void FAST_IO(string filein = "", string fileout = "", string fileerr = ""){
	if (fopen(filein.c_str(), "r")){
		freopen(filein.c_str(), "r", stdin);
		freopen(fileout.c_str(), "w", stdout);
#ifdef hollwo_pelw_local
		freopen(fileerr.c_str(), "w", stderr);
#endif
	}
	cin.tie(0), cout.tie(0) -> sync_with_stdio(0);
}

void Hollwo_Pelw();

signed main(){
#ifdef hollwo_pelw_local
	FAST_IO("input.inp", "output.out", "error.err");
	auto start = chrono::steady_clock::now();
#else
	FAST_IO("hollwo_pelw.inp", "hollwo_pelw.out");
#endif
	int testcases = 1;
	// cin >> testcases;
	for (int test = 1; test <= testcases; test++){
		// cout << "Case #" << test << ": ";
		Hollwo_Pelw();
	}
#ifdef hollwo_pelw_local
	auto end = chrono::steady_clock::now();
	cout << "\nExcution time : " << chrono::duration_cast<chrono::milliseconds> (end - start).count() << "[ms]" << endl;
#endif
	return 0;
}

const int N = 1e5 + 5;

struct edge_t {
	int u, v; char d = 'B';
} ed[N];

int n, m, q, tin[N], low[N], timer;
vector<pair<int, int>> adj[N];

int comp[N], compcnt;
vector<int> st;

void tarjan(int u, int p) {
	tin[u] = low[u] = ++ timer;
	st.push_back(u);

	for (auto [v, i] : adj[u]) if (i != p) {
		if (tin[v]) {
			low[u] = min(low[u], tin[v]);
		} else {
			tarjan(v, i);
			low[u] = min(low[u], low[v]);
		}
	}

	if (low[u] >= tin[u]) {
		++ compcnt;
		while (1) {
			int v = st.back();
			comp[v] = compcnt;

			st.pop_back();
			if (v == u) break ;
		}
	}
}

void __build_tree__() {
	for (int i = 1; i <= n; i++)
		adj[i].clear();

	for (int i = 1; i <= m; i++) {
		ed[i].u = comp[ed[i].u];
		ed[i].v = comp[ed[i].v];
		if (ed[i].u != ed[i].v) {
			adj[ed[i].u].emplace_back(ed[i].v, i);
			adj[ed[i].v].emplace_back(ed[i].u, i);
		}
	}

	n = compcnt;
}

int dp[N], vis[N];

void solve(int u, int p) {
	vis[u] = 1;

	for (auto [v, i] : adj[u]) if (v != p) {
		solve(v, u);

		if (dp[v] == 0)
			ed[i].d = 'B';
		else if (dp[v] < 0)
			ed[i].d = u == ed[i].u ? 'R' : 'L';
		else if (dp[v] > 0)
			ed[i].d = u == ed[i].u ? 'L' : 'R';

		dp[u] += dp[v];
	}
}

void Hollwo_Pelw() {
	cin >> n >> m;
	for (int i = 1, u, v; i <= m; i++) {
		cin >> u >> v, ed[i] = {u, v, 'B'};
		adj[u].emplace_back(v, i);
		adj[v].emplace_back(u, i);
	}

	for (int i = 1; i <= n; i++)
		if (!tin[i]) tarjan(i, 0);
	__build_tree__();

	cin >> q;
	for (int u, v; q --; )
		cin >> u >> v, dp[comp[u]] ++, dp[comp[v]] --;

	for (int i = 1; i <= n; i++)
		if (!vis[i]) solve(i, 0);

	for (int i = 1; i <= m; i++)
		cout << ed[i].d;
}

Compilation message (stderr)

oneway.cpp: In function 'void FAST_IO(std::string, std::string, std::string)':
oneway.cpp:18:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |   freopen(filein.c_str(), "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:19:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |   freopen(fileout.c_str(), "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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