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Submission #489487

# Submission time Handle Problem Language Result Execution time Memory
489487 2021-11-23T03:45:34 Z danielliu04 One-Way Streets (CEOI17_oneway) C++17
100 / 100
 158 ms 21928 KB 
// Link: https://cses.fi/problemset/task/1691

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

#define ll long long
#define lc (node<<1)+1
#define rc (node<<1)+2
#define endl '\n'
#define INF 1e9

const int max_n = 1e5+2;
int n, m, k;

pair<int, int> edges[max_n];
vector<int> adj[max_n];

int enter[max_n], low[max_n];
int t = 0;

int scc[max_n]; // stores the id of the strongly connected component
int id = 0;
stack<int> s;

vector<int> tree[max_n];
int dp[max_n];

void dfs(int node, int parent = -1){
    enter[node] = low[node] = t ++;
    s.push(node);

    bool pp = 0;
    for(int next : adj[node]){
        if(next != parent || pp){
            if(enter[next] == -1){
                dfs(next, node);
                low[node] = min(low[node], low[next]);
                if(low[next] == enter[next]){ // no edge going up 
                    while(true){
                        int a = s.top();
                        scc[a] = id;
                        s.pop();
                        if(a == next) break;
                    }
                    id ++;
                }
            }
            else{
                low[node] = min(low[node], enter[next]);
            }
        }
        else{
            pp = 1;
        }
    }
}

int depth[max_n];

void dfs2(int node, int parent = -1, int dep = 0){
    depth[node] = dep;
    for(int next: tree[node]){
        if(next == parent) continue;
        dfs2(next, node, dep + 1);
        dp[node] += dp[next];
    }
}

int main() {
    
    cin >> n >> m;
    for(int i = 0; i < m; i ++){
        int a, b; cin >> a >> b; a --; b --;
        adj[a].push_back(b); adj[b].push_back(a);
        edges[i] = {a, b};
    }

    // find 2-edge-connected-components and create a tree out of it
    // always direct the edges from top->bottom

    fill(enter, enter + n, -1);
    for(int i = 0; i < n; i ++){
        if(enter[i] == -1){
            dfs(i);
            while(!s.empty()){
                int a = s.top();
                s.pop();
                scc[a] = id;
            }
            id ++;
        }
    }


    for(int i = 0; i < m; i ++){
        int a = scc[edges[i].first], b = scc[edges[i].second];
        if(a == b) continue;
        tree[a].push_back(b);
        tree[b].push_back(a);
    }

    // now we loop through the required passages and assign values
    cin >> k;
    for(int i = 0; i < k; i ++){
        int a, b; cin >> a >> b; a --; b --;
        a = scc[a]; b = scc[b];
        dp[a]++; dp[b]--; // positive means going up, negative means going down
    }

    for(int i = 0; i < id; i ++){
        if(!depth[i]) dfs2(i);
    }

    for(int i = 0; i < m; i ++){
        int a = scc[edges[i].first], b = scc[edges[i].second];
        if(a == b) cout << 'B';
        else if(depth[b] > depth[a]){ // this means a is above b
            if(dp[b] < 0){
                cout << 'R';
            }
            else if(dp[b] == 0){
                cout << 'B';
            }
            else if(dp[b] > 0){
                cout << 'L';
            }
        }
        else{
            if(dp[a] < 0){
                cout << 'L';
            }
            else if(dp[a] == 0){
                cout << 'B';
            }
            else if(dp[a] > 0){
                cout << 'R';
            }
        }
    }

    cout << endl;
}

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 4940 KB Output is correct
2 Correct 3 ms 4940 KB Output is correct
3 Correct 4 ms 4972 KB Output is correct
4 Correct 3 ms 5012 KB Output is correct
5 Correct 4 ms 5068 KB Output is correct
6 Correct 5 ms 5016 KB Output is correct
7 Correct 4 ms 5068 KB Output is correct
8 Correct 5 ms 5068 KB Output is correct
9 Correct 4 ms 5012 KB Output is correct
10 Correct 4 ms 5068 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 4940 KB Output is correct
2 Correct 3 ms 4940 KB Output is correct
3 Correct 4 ms 4972 KB Output is correct
4 Correct 3 ms 5012 KB Output is correct
5 Correct 4 ms 5068 KB Output is correct
6 Correct 5 ms 5016 KB Output is correct
7 Correct 4 ms 5068 KB Output is correct
8 Correct 5 ms 5068 KB Output is correct
9 Correct 4 ms 5012 KB Output is correct
10 Correct 4 ms 5068 KB Output is correct
11 Correct 65 ms 10228 KB Output is correct
12 Correct 68 ms 11268 KB Output is correct
13 Correct 73 ms 12648 KB Output is correct
14 Correct 86 ms 14124 KB Output is correct
15 Correct 114 ms 14668 KB Output is correct
16 Correct 104 ms 15388 KB Output is correct
17 Correct 92 ms 17300 KB Output is correct
18 Correct 124 ms 15384 KB Output is correct
19 Correct 87 ms 18608 KB Output is correct
20 Correct 72 ms 11204 KB Output is correct
21 Correct 86 ms 10848 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 4940 KB Output is correct
2 Correct 3 ms 4940 KB Output is correct
3 Correct 4 ms 4972 KB Output is correct
4 Correct 3 ms 5012 KB Output is correct
5 Correct 4 ms 5068 KB Output is correct
6 Correct 5 ms 5016 KB Output is correct
7 Correct 4 ms 5068 KB Output is correct
8 Correct 5 ms 5068 KB Output is correct
9 Correct 4 ms 5012 KB Output is correct
10 Correct 4 ms 5068 KB Output is correct
11 Correct 65 ms 10228 KB Output is correct
12 Correct 68 ms 11268 KB Output is correct
13 Correct 73 ms 12648 KB Output is correct
14 Correct 86 ms 14124 KB Output is correct
15 Correct 114 ms 14668 KB Output is correct
16 Correct 104 ms 15388 KB Output is correct
17 Correct 92 ms 17300 KB Output is correct
18 Correct 124 ms 15384 KB Output is correct
19 Correct 87 ms 18608 KB Output is correct
20 Correct 72 ms 11204 KB Output is correct
21 Correct 86 ms 10848 KB Output is correct
22 Correct 148 ms 18328 KB Output is correct
23 Correct 158 ms 16444 KB Output is correct
24 Correct 153 ms 16580 KB Output is correct
25 Correct 140 ms 21928 KB Output is correct
26 Correct 141 ms 17852 KB Output is correct
27 Correct 149 ms 16636 KB Output is correct
28 Correct 70 ms 8040 KB Output is correct
29 Correct 118 ms 11768 KB Output is correct
30 Correct 115 ms 11976 KB Output is correct
31 Correct 123 ms 12380 KB Output is correct
32 Correct 132 ms 15768 KB Output is correct