제출 #1025082

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1025082		Szil	One-Way Streets (CEOI17_oneway)	C++17	0 / 100	2 ms	5212 KiB

oneway

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

const int MAXN = 100'001;

vector<pair<int, int>> g[MAXN], g2[MAXN];
int l[MAXN], tin[MAXN], timer = 1, cc = 0, comp[MAXN], be[MAXN], ki[MAXN], up[MAXN][22], fel[MAXN], le[MAXN], U[MAXN], V[MAXN];
char ans[MAXN];
bool is_bridge[MAXN];

void dfs(int u, int p = -1) {
	l[u] = tin[u] = timer++;
	for (auto [v, idx] : g[u]) {
		if (idx == p) continue;
		if (tin[v]) {
			l[u] = min(l[u], tin[v]);
		} else {
			dfs(v, idx);
			l[u] = min(l[u], l[v]);
			if (l[v] > tin[u]) {
				is_bridge[idx] = 1;
			}
		}
	}
}

void dfs2(int u) {
	comp[u] = cc;
	for (auto [v, idx] : g[u]) {
		if (is_bridge[idx] || comp[v]) continue;
		dfs2(v);
	}
}

void dfs3(int u, int p = -1) {
	if (p != -1) {
		up[u][0] = p;
		for (int i = 1; i < 21; i++) {
			up[u][i] = up[up[u][i-1]][i-1];
		}
	}
	be[u] = timer++;
	for (auto [v, idx] : g2[u]) {
		if (v == p) continue;
		dfs3(v, u);
	}
	ki[u] = timer++;
}

bool is_ancestor(int u, int v) {
	return be[u] <= be[v] && ki[v] <= ki[u];
}

int lca(int u, int v) {
	if (is_ancestor(u, v)) return u;
	if (is_ancestor(v, u)) return v;
	for (int i = 20; i >= 0; i--) {
		if (!is_ancestor(up[u][i], v)) u = up[u][i];
	}
	return up[u][0];
}

pair<int, int> dfs4(int u, int p = -1) {
	int x = 0, y = 0;
	for (auto [v, idx] : g2[u]) {
		if (v == p) continue;
		auto [a, b] = dfs4(v, u);
		if (a == 0 && b == 0) ans[idx] = 'B';
		else if (a) ans[idx] = v == V[idx] ? 'L' : 'R';
		else if (b) ans[idx] = v == V[idx] ? 'R' : 'L';
		x += a; y += b;
	}
	return {x + fel[u], y + le[u]};
}

int main() {
	ios::sync_with_stdio(0); cin.tie(0);
	int n, m; cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		cin >> U[i] >> V[i];
		g[U[i]].emplace_back(V[i], i);
		g[V[i]].emplace_back(U[i], i);
	}

	dfs(1);
	for (int i = 1; i <= n; i++) {
		if (!comp[i]) {
			cc++;
			dfs2(i);
		}
	}
	
	for (int i = 1; i <= n; i++) {
		for (auto [v, idx] : g[i]) {
			if (comp[v] != comp[i]) {
				g2[comp[i]].emplace_back(comp[v], idx);
			} else {
				ans[idx] = 'B';
			}
		}
	}

	dfs3(1);

	int q; cin >> q;
	while (q--) {
		int u, v; cin >> u >> v;
		u = comp[u]; v = comp[v];
		int x = lca(u, v);
		fel[u]++;
		le[v]++;
		fel[x]--;
		le[x]--;
	}

	dfs4(1);

	for (int i = 1; i <= m; i++) {
		cout << ans[i];
	}
	cout << "\n";
	return 0;
}

• Subtask 1: 0 / 30
• Subtask 2: 0 / 30
• Subtask 3: 0 / 40