Submission #5314043

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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< T > g) {
  T INF = numeric_limits< T >::max();

  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 < N; j++) {
      assert(g[i][j] == g[j][i]);
      if(g[i][j] > 0) {
        ++deg[i];
        ++M;
      }
    }
  }
  int lim = (int) sqrt(M);
  T ret = 0;
  for(int i = 0; i < N; i++) {
    int root = -1;
    for(int j = 0; j < N; j++) {
      if(v[j]) continue;
      if(root == -1 || deg[j] < deg[root]) root = j;
    }
    vector< int > rots;
    for(int j = 0; j < N; j++) {
      if(j != root && g[root][j] > 0) rots.emplace_back(j);
    }
    if(rots.size() >= lim) {
      vector< int > rest;
      for(int j = 0; j < N; j++) {
        if(!v[j]) rest.emplace_back(j);
      }
      vector< vector< T > > dp(1 << rest.size(), vector< T >(rest.size(), INF));
      for(int j = 1; j < (1 << rest.size()); j++) {
        int add = __builtin_ctz(j);
        int base = j - (1 << add);
        if(base == 0) continue;
        T sum = 0;
        for(int k = add + 1; k < rest.size(); k++) {
          if((j >> k) & 1) {
            dp[j][add] = min(dp[j][add], g[rest[k]][rest[add]]);
            dp[j][k] = min(dp[base][k], g[rest[k]][rest[add]]);
            sum += dp[j][k];
          }
        }
        ret = max(ret, sum + dp[j][add]);
      }
      break;
    }
    vector< vector< T > > dp(1 << rots.size(), vector< T >(rots.size() + 1, INF));
    for(int j = 1; j < (1 << rots.size()); j++) {
      int add = __builtin_ctz(j);
      int base = j - (1 << add);
      T sum = 0;

      dp[j][add] = g[rots[add]][root];
      dp[j][rots.size()] = min(dp[base][rots.size()], dp[j][add]);

      for(int k = add + 1; k < rots.size(); k++) {
        if((j >> k) & 1) {
          dp[j][add] = min(dp[j][add], g[rots[k]][rots[add]]);
          dp[j][k] = min(dp[base][k], g[rots[k]][rots[add]]);
          sum += dp[j][k];
        }
      }
      ret = max(ret, sum + dp[j][add] + dp[j][rots.size()]);
    }

    v[root] = true;
    for(int j = 0; j < N; j++) {
      if(g[j][root] > 0) {
        --deg[j];
        g[root][j] = g[j][root] = 0;
      }
    }
  }
  return ret;
}


int main() {
  int N, M;
  cin >> N >> M;
  Matrix< int > g(N, vector< int >(N));
  for(int i = 0; i < M; i++) {
    int x, y;
    cin >> x >> y;
    --x, --y;
    g[x][y] = 1;
    g[y][x] = 1;
  }
  cout << max(1, maximum_clique(g)) << endl;
}

Submission Info

Judge Result