Submission #1052337

#	Time	Username	Problem	Language	Result	Execution time	Memory
1052337		abczz	Parachute rings (IOI12_rings)	C++17	100 / 100	2062 ms	218344 KiB

rings

#include <iostream>
#include <map>
#include <vector>
#include <queue>
#define ll long long

using namespace std;

map <ll, ll> mp;
bool ok;
ll visited[1000000], cur;
vector <ll> adj[1000000], V, U;
queue <ll> Q;
ll n, x, y, z, tot, P[1000000], cyc[1000000], deg[1000000];
ll dsu(ll u) {
  if (P[u] == u) return u;
  else return P[u] = dsu(P[u]);
}
void Init(int N_) {
  ok = 0;
  n = N_;
  tot = 0;
  mp.clear();
  for (int i=0; i<n; ++i) {
    adj[i].clear();
    P[i] = i;
    ++mp[i];
  }
}

void dfs(ll u, ll p) {
  visited[u] = cur;
  V.push_back(u);
  for (auto v : adj[u]) {
    if (visited[v] != cur) dfs(v, u);
    else if (v != p) {
      U.clear();
      for (int i=V.size()-1; i>=0; --i) {
        //cout << V[i] << "*";
        if (mp.count(V[i])) U.push_back(V[i]);
        if (V[i] == v) break;
      }
      //cout << endl;
      mp.clear();
      for (auto u : U) ++mp[u];
    }
  }
  visited[u] = -1;
  V.pop_back();
}

void relabel(ll u, ll p, ll w) {
  P[u] = w;
  visited[u] = cur;
  for (auto v : adj[u]) {
    if (visited[v] != cur && v != z) {
      relabel(v, u, w);
    }
  }
}

void Link(int A, int B) {
  if (mp.empty()) return;
  else if (ok) {
    if (A == z || B == z) return;
    if (deg[A] == 2 || deg[B] == 2) {
      mp.clear();
      return;
    }
    ++deg[A], ++deg[B];
    x = dsu(A), y = dsu(B);
    if (x == y) mp.clear();
    P[x] = y;
    return;
  }
  ++deg[A], ++deg[B];
  adj[A].push_back(B);
  adj[B].push_back(A);
  x = dsu(A), y = dsu(B);
  if (x == y) {
    ++cyc[x];
    if (cyc[x] <= 2) {
      V.clear();
      ++cur;
      dfs(A, -1);
    }
    else ok = 1;
  }
  else {
    P[x] = y;
    if (cyc[x] && cyc[y]) {
      mp.clear();
      return;
    }
    cyc[y] += cyc[x];
  }
  //cout << A << " " << B << " " << tot << endl;
  if (deg[A] > 3) {
    if (mp.count(A)) {
      mp.clear();
      ++mp[A];
    }
    else mp.clear();
  }
  else if (deg[A] == 3) {
    V.clear();
    if (mp.count(A)) V.push_back(A);
    for (auto v : adj[A]) {
      if (mp.count(v)) V.push_back(v);
    }
    mp.clear();
    for (auto u : V) ++mp[u];
  }
  if (deg[B] > 3) {
    if (mp.count(B)) {
      mp.clear();
      ++mp[B];
    }
    else mp.clear();
  }
  else if (deg[B] == 3) {
    V.clear();
    if (mp.count(B)) V.push_back(B);
    for (auto v : adj[B]) {
      if (mp.count(v)) V.push_back(v);
    }
    mp.clear();
    for (auto u : V) ++mp[u];
  }
  if (ok) {
    if (mp.size() > 1) {
      mp.clear();
      return;
    }
    for (auto [x, y] : mp) {
      z = x;
      for (auto v : adj[x]) {
        --deg[v];
      }
    }
    ++cur;
    tot = 0;
    for (int i=0; i<n; ++i) {
      if (i == z) continue;
      if (deg[i] <= 1) {
        Q.push(i);
        visited[i] = cur;
      }
      else if (deg[i] > 2) {
        mp.clear();
        return;
      }
    }
    while (!Q.empty()) {
      auto u = Q.front();
      Q.pop();
      ++tot;
      for (auto v : adj[u]) {
        if (v == z) continue;
        if (visited[v] != cur) {
          visited[v] = cur;
          Q.push(v);
        }
      }
    }
    if (tot != n-1) mp.clear();
    for (int i=0; i<n; ++i) {
      if (i == z) continue;
      if (deg[i] <= 1) {
        ++cur;
        relabel(i, -1, i);
      }
    }
  }
}

int CountCritical() {
  return mp.size();
}

• Subtask 1: 20 / 20
• Subtask 2: 17 / 17
• Subtask 3: 18 / 18
• Subtask 4: 14 / 14
• Subtask 5: 31 / 31