Submission #5400431

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Source Code Expand

#include<bits/stdc++.h>

using namespace std;

using int64 = long long;
const int mod = 1e9 + 7;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename T >
struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }

  operator int() const { return to; }
};

template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WeightedGraph = vector< Edges< T > >;
using UnWeightedGraph = vector< vector< int > >;
template< typename T >
using Matrix = vector< vector< T > >;

template< typename T >
T maximum_clique(Matrix< bool > g, function< T(vector< int >) > f) {

  int N = (int) g.size(), M = 0;
  vector< int > deg(N), v(N);
  for(int i = 0; i < N; i++) {
    for(int j = 0; j < i; j++) {
      assert(g[i][j] == g[j][i]);
      if(g[i][j]) {
        ++deg[i];
        ++M;
      }
    }
  }
  T t = 0;
  int lim = (int) sqrt(2 * M);

  for(int i = 0; i < N; i++) {
    vector< int > notice;
    for(int j = 0; j < N; j++) {
      if(!v[j] && deg[j] < lim) {
        for(int k = 0; k < N; k++) {
          if(j == k) continue;
          if(g[j][k]) notice.emplace_back(k);
        }
        notice.emplace_back(j);
        break;
      }
    }
    if(notice.empty()) break;
    int neighbor = (int) notice.size() - 1;
    vector< int > bit(neighbor);
    for(int j = 0; j < neighbor; j++) {
      for(int k = 0; k < j; k++) {
        if(!g[notice[j]][notice[k]]) {
          bit[j] |= 1 << k;
          bit[k] |= 1 << j;
        }
      }
    }
    for(int j = 0; j < (1 << neighbor); j++) {
      bool ok = true;
      for(int k = 0; k < neighbor; k++) {
        if((j >> k) & 1) ok &= (j & bit[k]) == 0;
      }
      if(ok) {
        vector< int > stock{notice.back()};
        for(int k = 0; k < neighbor; k++) {
          if((j >> k) & 1) stock.emplace_back(notice[k]);
        }
        t = max(t, f(stock));
      }
    }
    v[notice.back()] = true;
    for(int j = 0; j < N; j++) {
      if(g[j][notice.back()]) {
        --deg[j];
        g[notice.back()][j] = g[j][notice.back()] = false;
      }
    }
  }

  vector< int > notice;
  for(int j = 0; j < N; j++) {
    if(!v[j]) notice.emplace_back(j);
  }
  int neighbor = (int) notice.size();
  vector< int > bit(neighbor);
  for(int j = 0; j < neighbor; j++) {
    for(int k = 0; k < j; k++) {
      if(!g[notice[j]][notice[k]]) {
        bit[j] |= 1 << k;
        bit[k] |= 1 << j;
      }
    }
  }
  for(int j = 0; j < (1 << neighbor); j++) {
    bool ok = true;
    for(int k = 0; k < neighbor; k++) {
      if((j >> k) & 1) ok &= (j & bit[k]) == 0;
    }
    if(ok) {
      vector< int > stock;
      for(int k = 0; k < neighbor; k++) {
        if((j >> k) & 1) stock.emplace_back(notice[k]);
      }
      t = max(t, f(stock));
    }
  }
  return t;
}

int main() {
  int N, M;
  cin >> N >> M;
  Matrix< bool > g(N, vector< bool >(N));
  for(int i = 0; i < M; i++) {
    int x, y;
    cin >> x >> y;
    --x, --y;
    g[x][y] = true;
    g[y][x] = true;
  }
  function< int(vector< int >) > f = [](vector< int > t) { return t.size(); };
  cout << maximum_clique(g, f) << endl;
}

Submission Info

Judge Result