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Submission #1059189

# Submission time Handle Problem Language Result Execution time Memory
1059189 2024-08-14T18:23:12 Z vjudge1 One-Way Streets (CEOI17_oneway) C++17
100 / 100
 92 ms 42896 KB 
#include <bits/stdc++.h>
using namespace std;

#define ff first
#define ss second
#define pb push_back

typedef long long ll;
typedef pair <int,int> pii;

const ll N = 1e5 + 5;
const ll S = 2010;
const ll LOG_N = 18;
const ll oo = 1e16+7;
const ll mod = 2e9 + 7;

char ans[N];
pii edges[N];
vector <vector<pii>> bridge_tree;
int up[N], down[N];
int tin[N], tout[N];
int st[N][20];
int visi[N];
int cnt = 0;

struct tarjan_tree {
  int n;
  vector<vector<int>> comps;
  vector<vector<pii>> g;
  vector<pair<pii, int>> bridge;
  vector<int> id, art;
  tarjan_tree(int n) : n(n), g(n+1), id(n+1), art(n+1) {}
  void add_edge(vector<vector<pii>> &g, int u, int v, int idx) { /// nodes from [1, n]
    g[u].push_back({v, idx});
    g[v].push_back({u, idx});
  }
  void add_edge(int u, int v, int idx) { add_edge(g, u, v, idx); }
  void tarjan(bool with_bridge) {
    vector<int> dfn(n+1), low(n+1);
    stack<int> st;
    comps.clear();
    function<void(int, int, int&)> dfs = [&](int u, int p, int &t) {
      dfn[u] = low[u] = ++t;
      st.push(u);
      int cntp = 0;
      for(auto [v, idx] : g[u]) {
        cntp += v == p;
        if(!dfn[v])	{
          dfs(v, u, t);
          low[u] = min(low[u], low[v]);
          if(with_bridge && low[v] > dfn[u]) {
            bridge.push_back(make_pair(make_pair(min(u,v), max(u,v)), idx));
            comps.push_back({});
            for(int w = -1; w != v; )
              comps.back().push_back(w = st.top()), st.pop();
          }
          if(!with_bridge && low[v] >= dfn[u]) {
            art[u] = (dfn[u] > 1 || dfn[v] > 2);
            comps.push_back({u});
            for(int w = -1; w != v; )
              comps.back().push_back(w = st.top()), st.pop();
          }
        }
        else if(v != p || cntp > 1) low[u] = min(low[u], dfn[v]);
      }
      if(p == -1 && ( with_bridge || g[u].size() == 0 )) {
        comps.push_back({});
        for(int w = -1; w != u; )
          comps.back().push_back(w = st.top()), st.pop();
      }
    };
    for(int u = 1, t; u <= n; ++u)
      if(!dfn[u]) dfs(u, -1, t = 0);
  }
  vector<vector<pii>> build_bridge_tree() {
    tarjan(true);
    vector<vector<pii>> tree(comps.size());
    for(int i = 0; i < comps.size(); ++i)
      for(int u : comps[i]) id[u] = i;
    for(auto &b : bridge)
      add_edge(tree, id[b.ff.ff], id[b.ff.ss], b.ss);
    return tree;
  }
};

void dfs (int u, int p) { 
  st[u][0] = p;
  visi[u] = 1;
  tin[u] = cnt++;
  for (auto &v : bridge_tree[u]) { 
    if (v.ff == p) continue;
    dfs(v.ff, u);
  }
  tout[u] = cnt - 1;
}

bool anc (int u, int v) { 
  if (tin[u] <= tin[v] && tout[v] <= tout[u]) return true;
  return false;
}

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

  for (int i = 19; i >= 0; --i) { 
    if (!anc(st[u][i], v))
      u = st[u][i];
  }
  return st[u][0];
}

void solve (int u, int p, int id) { 
  visi[u] = 1;
  for (auto &v : bridge_tree[u]) { 
    if (v.ff == p) continue;
    solve (v.ff, u, v.ss);
    up[u] += up[v.ff];
    down[u] += down[v.ff];
  }

  assert(up[u] == 0 || down[u] == 0);

  if (up[u]) {
    if (u == edges[id].ff) ans[id] = 'R';
    else ans[id] = 'L';
  }
  if (down[u]) {
    if (p == edges[id].ff) ans[id] = 'R';
    else ans[id] = 'L';
  }
}

int main () {
        
  #ifdef LOCAL
  freopen("input.txt","r",stdin);
  #endif

  ios_base::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);

  int n, m, p; 
  cin >> n >> m;

  

  tarjan_tree tj(n);
  for (int i = 0; i < m; ++i) {
    int a, b; cin >> a >> b;
    ans[i] = 'B';
    edges[i] = {a, b};
    if (a == b) {
      continue;
    }
    else {
      tj.add_edge(a, b, i);
    }
  }

  bridge_tree = tj.build_bridge_tree();


  int nn = bridge_tree.size();

  for (int i = 0; i < nn; ++i)
    if (!visi[i]) dfs(i,i);

  for (int i = 1; i < 20; ++i) { 
    for (int j = 0; j < nn; ++j) { 
      st[j][i] = st[st[j][i-1]][i-1];
    }
  }

  cin >> p;

  for (int i = 0; i < p; ++i) { 
    int u, v; cin >> u >> v;
    u = tj.id[u], v = tj.id[v];

    int lc = lca(u, v);

    //cout << u << " " << v << " " << lc << '\n';

    up[u]++;
    up[lc]--;
    down[v]++;
    down[lc]--;
  }

  for (int i = 0; i < m; ++i) {
    edges[i].ff = tj.id[edges[i].ff];
    edges[i].ss = tj.id[edges[i].ss];
  }

  memset(visi, 0, sizeof visi);
  for (int i = 0; i < nn; ++i) {
    if (!visi[i]) solve(i,i,-1);
  }

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

  return 0;
}

Compilation message

oneway.cpp: In member function 'std::vector<std::vector<std::pair<int, int> > > tarjan_tree::build_bridge_tree()':
oneway.cpp:78:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |     for(int i = 0; i < comps.size(); ++i)
      |                    ~~^~~~~~~~~~~~~~

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 860 KB Output is correct
2 Correct 0 ms 684 KB Output is correct
3 Correct 1 ms 856 KB Output is correct
4 Correct 1 ms 1116 KB Output is correct
5 Correct 1 ms 1116 KB Output is correct
6 Correct 0 ms 860 KB Output is correct
7 Correct 1 ms 1116 KB Output is correct
8 Correct 1 ms 1116 KB Output is correct
9 Correct 1 ms 928 KB Output is correct
10 Correct 0 ms 860 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 860 KB Output is correct
2 Correct 0 ms 684 KB Output is correct
3 Correct 1 ms 856 KB Output is correct
4 Correct 1 ms 1116 KB Output is correct
5 Correct 1 ms 1116 KB Output is correct
6 Correct 0 ms 860 KB Output is correct
7 Correct 1 ms 1116 KB Output is correct
8 Correct 1 ms 1116 KB Output is correct
9 Correct 1 ms 928 KB Output is correct
10 Correct 0 ms 860 KB Output is correct
11 Correct 21 ms 9308 KB Output is correct
12 Correct 25 ms 11308 KB Output is correct
13 Correct 30 ms 13852 KB Output is correct
14 Correct 40 ms 19764 KB Output is correct
15 Correct 46 ms 22220 KB Output is correct
16 Correct 47 ms 31912 KB Output is correct
17 Correct 53 ms 35244 KB Output is correct
18 Correct 54 ms 31764 KB Output is correct
19 Correct 59 ms 37700 KB Output is correct
20 Correct 23 ms 10580 KB Output is correct
21 Correct 21 ms 9940 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 860 KB Output is correct
2 Correct 0 ms 684 KB Output is correct
3 Correct 1 ms 856 KB Output is correct
4 Correct 1 ms 1116 KB Output is correct
5 Correct 1 ms 1116 KB Output is correct
6 Correct 0 ms 860 KB Output is correct
7 Correct 1 ms 1116 KB Output is correct
8 Correct 1 ms 1116 KB Output is correct
9 Correct 1 ms 928 KB Output is correct
10 Correct 0 ms 860 KB Output is correct
11 Correct 21 ms 9308 KB Output is correct
12 Correct 25 ms 11308 KB Output is correct
13 Correct 30 ms 13852 KB Output is correct
14 Correct 40 ms 19764 KB Output is correct
15 Correct 46 ms 22220 KB Output is correct
16 Correct 47 ms 31912 KB Output is correct
17 Correct 53 ms 35244 KB Output is correct
18 Correct 54 ms 31764 KB Output is correct
19 Correct 59 ms 37700 KB Output is correct
20 Correct 23 ms 10580 KB Output is correct
21 Correct 21 ms 9940 KB Output is correct
22 Correct 76 ms 36472 KB Output is correct
23 Correct 72 ms 32932 KB Output is correct
24 Correct 71 ms 32928 KB Output is correct
25 Correct 70 ms 42896 KB Output is correct
26 Correct 92 ms 35492 KB Output is correct
27 Correct 76 ms 33096 KB Output is correct
28 Correct 16 ms 4956 KB Output is correct
29 Correct 31 ms 10620 KB Output is correct
30 Correct 40 ms 10956 KB Output is correct
31 Correct 35 ms 11888 KB Output is correct
32 Correct 42 ms 21836 KB Output is correct