Submission #1093030

#	Time	Username	Problem	Language	Result	Execution time	Memory
1093030		BF001	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	85 ms	30848 KiB

oneway

#include<bits/stdc++.h>
using namespace std;
 
#define N 100005
#define fi first
#define se second  

typedef pair<int, int> ii;

int low[N], id[N], cnt, ncc, val[N], typ[N], n, m, dep[N];
vector<int> adj[N];
set<int> adj2[N];
stack<int> st;
vector<ii> eg;
 
void dfs(int u, int p){
    low[u] = id[u] = ++cnt;
    st.push(u);

    for (auto x : adj[u]){
        if (x == p){
            p = -1;
            continue;
        }
        if (id[x]){
            low[u] = min(low[u], id[x]);
        }
        else{
            dfs(x, u);
            low[u] = min(low[u], low[x]);
        }
    }

    if (id[u] == low[u]){
        ncc++;
        int s = -1;
        while (s != u){
            s = st.top();
            st.pop();
            typ[s] = ncc;
            low[s] = id[s] = n + 1;
        }
    }

} 

void getdep(int u, int p){
    for (auto x : adj2[u]){
        if (x == p) continue;
        dep[x] = dep[u] + 1;
        getdep(x, u);
        val[u] += val[x];
    }
}

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
 
    cin >> n >> m;
    for (int i = 1; i <= m; i++){
        int u, v;
        cin >> u >> v;
        eg.push_back({u, v});
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    for (int i = 1; i <= n; i++){
        if (!id[i]) dfs(i, 0);
        for (auto x : adj[i]){
            if (typ[x] != typ[i]){
                adj2[typ[x]].insert(typ[i]);
                adj2[typ[i]].insert(typ[x]);
            }
        }
    }

    int q;
    cin >> q;
    while (q--){
        int a, b;
        cin >> a >> b;
        val[typ[a]]++;
        val[typ[b]]--;
    }

    for (int i = 1; i <= ncc; i++){
        if (!dep[i]){
            dep[i] = 1;
            getdep(i, 0);
        }
    }

    for (auto x : eg){
        int a = typ[x.fi], b = typ[x.se];
        if (a == b){
            cout << "B";
            continue;
        }
        if (dep[a] > dep[b]){
            if (val[a] == 0){
                cout << "B";
            }
            if (val[a] > 0){
                cout << "R";
            }
            if (val[a] < 0){
                cout << "L";
            }
        }
        if (dep[a] < dep[b]){
            if (val[b] == 0){
                cout << "B";
            }
            if (val[b] > 0){
                cout << "L";
            }
            if (val[b] < 0){
                cout << "R";
            }
        }
    }
    
    return 0;
}

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