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Submission #921315

# Submission time Handle Problem Language Result Execution time Memory
921315 2024-02-03T17:03:47 Z Lecorbio One-Way Streets (CEOI17_oneway) C++14
100 / 100
 127 ms 34488 KB 
#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;
typedef long long ll;

const int N = 1e5+10;
const int P = 20;

int n, m;
pair<int,int> edge[N];
vector<pair<int,int>> g[N];

int tin[N], tout[N], low[N];
bool vis[N], bridge[N];
int comp[N];
vector<pair<int,int>> gc[N];

int depth[N];
pair<int,int> parent[N];
int up[N][P+3];
int path[N][3];
int direction[N];
char label[N];


///drewo dwuspojnych
int timer = 0;
void dfs_low(int v, int p){
    vis[v] = true;
    tin[v] = low[v] = ++timer;

    for (auto u : g[v]){
        if (u.se == p) continue;
        if (vis[u.fi]){
            low[v] = min(low[v], tin[u.fi]);
        }else{
            dfs_low(u.fi, u.se);
            low[v] = min(low[v], low[u.fi]);
            if (low[u.fi] > tin[v]) bridge[u.se] = true;
        }
    }
}

void components(int v, int c){
    vis[v] = true;
    comp[v] = c;
    for (auto u : g[v]){
        if (!vis[u.fi] && !bridge[u.se]){
            components(u.fi, c);
        }
    }
}


///LCA
int order = 0;
void dfs_lca(int v, int p, int idx){
    vis[v] = true;
    tin[v] = ++order;
    up[v][0] = p;
    parent[v] = {p, idx};

    for (int i=1; i<=P; i++){
        up[v][i] = up[up[v][i-1]][i-1];
    }

    for (auto u : gc[v]){
        if (u.fi != p){
            depth[u.fi] = depth[v] + 1;
            dfs_lca(u.fi, v, u.se);
        }
    }
    tout[v] = order;
}

bool is_ancestor(int u, int v){
    return tin[u] <= tin[v] && tout[u] >= tout[v];
}

int lca(int u, int v){
    if (is_ancestor(u, v)) return u;
    if (is_ancestor(v, u)) return v;

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


///skierowanie krawedzi
void direct(int x, int z, int dir){
    if (x == z) return;
    if (direction[x] == 0){
        direction[x] = dir;
        int p = parent[x].fi;
        int idx = parent[x].se;
        int a = comp[edge[idx].fi];
        int b = comp[edge[idx].se];

        if (dir == -1){
            if (a == x && b == p) label[idx] = 'R';
            else label[idx] = 'L';
        }else{
            if (a == x && b == p) label[idx] = 'L';
            else label[idx] = 'R';
        }
        direct(p, z, dir);
    }
}


int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    cin >> n >> m;
    for (int i=0; i<m; i++){
        int a, b; cin >> a >> b;
        edge[i] = {a, b};
        g[a].push_back({b, i});
        g[b].push_back({a, i});
    }

    //drzewo dwuspojnych
    for (int i=1; i<=n; i++){
        if (!vis[i]) dfs_low(i, -1);
    }

    for (int i=1; i<=n; i++) vis[i] = false;
    int c = 1;
    for (int i=1; i<=n; i++){
        if (!vis[i]){
            components(i, c);
            c++;
        }
    }

    for (int i=0; i<m; i++){
        if (bridge[i]){
            int ca = comp[edge[i].fi];
            int cb = comp[edge[i].se];
            gc[ca].push_back({cb, i});
            gc[cb].push_back({ca, i});
        }
    }
    /*
    cout << '\n';
    for (int i=1; i<=n; i++){
        cout << i << ": ";
        for (auto ele : gc[i]) cout << ele.fi << ' ';
        cout << '\n';
    }
    */

    //lca
    for (int i=1; i<=n; i++) vis[i] = false;
    for (int i=1; i<=n; i++){
        if (!vis[i]){
            depth[i] = 1;
            dfs_lca(i, i, 0);
        }
    }

    //skierowanie krawedzi
    for (int i=0; i<m; i++) label[i] = 'B';
    vector<pair<int,int>> ord;
    int q; cin >> q;
    for (int i=0; i<q; i++){
        int a, b; cin >> a >> b;
        path[i][0] = comp[a];
        path[i][1] = comp[b];
        path[i][2] = lca(comp[a], comp[b]);
        ord.push_back({depth[path[i][2]], i});
    }

    sort(ord.begin(), ord.end());
    for (auto ele : ord){
        int a = path[ele.se][0];
        int b = path[ele.se][1];
        int lc = path[ele.se][2];
        direct(a, lc, -1);
        direct(b, lc, 1);
    }

    for (int i=0; i<m; i++) cout << label[i];
    cout << '\n';

    return 0;
}
/*

10 10
7 6
4 1
6 6
10 10
6 6
4 1
1 7
7 6
6 8
8 10
0


5 6
1 2
1 2
4 3
2 3
1 3
5 1
2
4 5
1 3

*/

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 10584 KB Output is correct
2 Correct 2 ms 10588 KB Output is correct
3 Correct 2 ms 10588 KB Output is correct
4 Correct 2 ms 10588 KB Output is correct
5 Correct 3 ms 10588 KB Output is correct
6 Correct 2 ms 10588 KB Output is correct
7 Correct 3 ms 10588 KB Output is correct
8 Correct 3 ms 10588 KB Output is correct
9 Correct 3 ms 10588 KB Output is correct
10 Correct 2 ms 10588 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 10584 KB Output is correct
2 Correct 2 ms 10588 KB Output is correct
3 Correct 2 ms 10588 KB Output is correct
4 Correct 2 ms 10588 KB Output is correct
5 Correct 3 ms 10588 KB Output is correct
6 Correct 2 ms 10588 KB Output is correct
7 Correct 3 ms 10588 KB Output is correct
8 Correct 3 ms 10588 KB Output is correct
9 Correct 3 ms 10588 KB Output is correct
10 Correct 2 ms 10588 KB Output is correct
11 Correct 29 ms 18268 KB Output is correct
12 Correct 34 ms 21076 KB Output is correct
13 Correct 39 ms 22100 KB Output is correct
14 Correct 49 ms 27100 KB Output is correct
15 Correct 52 ms 27340 KB Output is correct
16 Correct 66 ms 27984 KB Output is correct
17 Correct 78 ms 29520 KB Output is correct
18 Correct 80 ms 28068 KB Output is correct
19 Correct 75 ms 30548 KB Output is correct
20 Correct 35 ms 20564 KB Output is correct
21 Correct 34 ms 20308 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 10584 KB Output is correct
2 Correct 2 ms 10588 KB Output is correct
3 Correct 2 ms 10588 KB Output is correct
4 Correct 2 ms 10588 KB Output is correct
5 Correct 3 ms 10588 KB Output is correct
6 Correct 2 ms 10588 KB Output is correct
7 Correct 3 ms 10588 KB Output is correct
8 Correct 3 ms 10588 KB Output is correct
9 Correct 3 ms 10588 KB Output is correct
10 Correct 2 ms 10588 KB Output is correct
11 Correct 29 ms 18268 KB Output is correct
12 Correct 34 ms 21076 KB Output is correct
13 Correct 39 ms 22100 KB Output is correct
14 Correct 49 ms 27100 KB Output is correct
15 Correct 52 ms 27340 KB Output is correct
16 Correct 66 ms 27984 KB Output is correct
17 Correct 78 ms 29520 KB Output is correct
18 Correct 80 ms 28068 KB Output is correct
19 Correct 75 ms 30548 KB Output is correct
20 Correct 35 ms 20564 KB Output is correct
21 Correct 34 ms 20308 KB Output is correct
22 Correct 127 ms 31496 KB Output is correct
23 Correct 125 ms 30188 KB Output is correct
24 Correct 110 ms 30140 KB Output is correct
25 Correct 115 ms 34488 KB Output is correct
26 Correct 114 ms 31108 KB Output is correct
27 Correct 117 ms 30152 KB Output is correct
28 Correct 27 ms 15600 KB Output is correct
29 Correct 59 ms 22080 KB Output is correct
30 Correct 61 ms 22232 KB Output is correct
31 Correct 53 ms 22496 KB Output is correct
32 Correct 72 ms 27340 KB Output is correct