제출 #1308852

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1308852		Balsa	One-Way Streets (CEOI17_oneway)	C++17	60 / 100	3095 ms	24084 KiB

oneway

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

#define all(x) (x).begin(), (x).end()
#define fi first
#define se second

using ll = long long;
const ll MAXN = 100005;
const ll MAXM = 100005;

vector<tuple<ll, ll, char>> edges[MAXN];
bool vis[MAXN];
ll tin[MAXN], low[MAXN];
bool is_bridge[MAXM];
ll timer = 0;

ll who[MAXN];
ll comp_num = 1;
stack<ll> st;

void find_bridges(ll v, ll peid) {
    if (vis[v]) return;
    vis[v] = 1;

    tin[v] = low[v] = timer++;
    st.push(v);

    for (auto[u, id, dir] : edges[v]) {
        if (id == peid) continue;
        if (!vis[u]) {
            find_bridges(u, id);
            low[v] = min(low[v], low[u]);
            if (low[u] > tin[v]) {
                is_bridge[id] = 1;
                while (1) {
                    ll x = st.top();
                    st.pop();
                    who[x] = comp_num;
                    if (x == u) break;
                }
                comp_num++;
            }
        } else {
            low[v] = min(low[v], tin[u]);
        }
    }
}

vector<tuple<ll, ll, char>> tecc_edges[MAXN];
string ans;

bool dfs(ll v, ll p, ll dest) {
    if (v == dest) return true;

    for (auto[u, id, dir] : tecc_edges[v]) {
        if (u == p) continue;
        if (dfs(u, v, dest)) {
            ans[id] = dir;
            return true;
        }
    }

    return false;
}

void solve() {
    ll n, m;
    cin >> n >> m;
    for (ll i = 0; i < m; i++) {
        ll v, u;
        cin >> v >> u;
        v--, u--;
        edges[v].push_back({u, i, 'R'});
        edges[u].push_back({v, i, 'L'});
    }

    for (ll v = 0; v < n; v++) tin[v] = low[v] = 1e18;

    for (ll v = 0; v < n; v++) {
        if (vis[v]) continue;
        find_bridges(v, -1);
    }

    for (ll v = 0; v < n; v++) {
        for (auto[u, id, dir] : edges[v]) {
            if (who[v] == who[u]) continue;
            tecc_edges[who[v]].push_back({who[u], id, dir});
        }
    }

    ans.assign(m, 'B');

    ll q; cin >> q;
    while (q--) {
        ll v, u;
        cin >> v >> u;
        v--, u--;
        dfs(who[v], -1, who[u]);
    }

    cout << ans << '\n';
}

int main() {
    // freopen("promote.in", "r", stdin);
    // freopen("promote.out", "w", stdout);
 
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    solve();
}

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