Submission #115067

#	Time	Username	Problem	Language	Result	Execution time	Memory
115067		minhtung0404	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	157 ms	25180 KiB

oneway

//https://csacademy.com/contest/ceoi-2017-day-1/task/one-way-streets/statement/

#include<bits/stdc++.h>
const int N = 1e5 + 5;
using namespace std;

struct edge{
    int u, v, id;

    edge(int u, int v, int id) : u(u), v(v), id(id) {}
    edge() {}
};

vector <edge> mv;
typedef pair <int, int> ii;
vector <ii> G[N], G2[N];

int n, m, q, pset[N];
int num[N], low[N], cnt, d[N], ans[N];
bool visited[N];
ii p[N];

int Find(int i) {return ((pset[i] == i) ? i : pset[i] = Find(pset[i]));}

void dsu(int u, int v){
    u = Find(u); v = Find(v);
    if (u == v) return;
    pset[v] = u;
}

void dfs(int u, int id){
    num[u] = low[u] = ++cnt;
    for (auto p : G[u]){
        int v = p.first;
        if (id == abs(p.second)) continue;
        if (num[v]) {
            low[u] = min(low[u], num[v]);
            dsu(u, v);
        }
        else {
            dfs(v, abs(p.second));
            low[u] = min(low[u], low[v]);
            if (low[v] <= num[u]) dsu(u, v);
            else{
                mv.push_back(edge(u, v, p.second));
            }
        }
    }
}

void redfs(int u){
    visited[u] = true;
    for(auto x : G2[u]){
        int v = x.first;
        if (visited[v]) continue;
        p[v].first = u; p[v].second = -x.second;
        d[v] = d[u] + 1;
        redfs(v);
    }
}

int main(){
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= n; i++) pset[i] = i;
    for (int i = 1; i <= m; i++){
        int u, v;
        cin >> u >> v;
        G[u].push_back(ii(v, i));
        G[v].push_back(ii(u, -i));
    }
    cin >> q;
    for (int i = 1; i <= n; i++) if (!num[i]) dfs(i, 0);
    for (auto ed : mv){
        ed.u = Find(ed.u); ed.v = Find(ed.v);
        G2[ed.u].push_back(ii(ed.v, ed.id));
        G2[ed.v].push_back(ii(ed.u, -ed.id));
    }
    for (int i = 1; i <= n; i++) if (pset[i] == i && !visited[i]) redfs(i);
    while (q--){
        int u, v;
        cin >> u >> v;
        u = Find(u); v = Find(v);
        while (u != v){
            if (d[u] > d[v]) {
                dsu(p[u].first, u);
                ans[abs(p[u].second)] = ((p[u].second > 0) ? 1 : 2);
                u = Find(p[u].first);
            }
            else{
                dsu(p[v].first, v);
                ans[abs(p[v].second)] = ((p[v].second > 0) ? 2 : 1);
                v = Find(p[v].first);
            }
        }
    }
    for (int i = 1; i <= m; i++){
        if (ans[i] == 0) cout << "B";
        if (ans[i] == 1) cout << "R";
        if (ans[i] == 2) cout << "L";
    }
}

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