Submission #4074904

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Source Code Expand

#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0, max_i = (n); i < max_i; i++)
#define REPI(i, a, b) for (int i = (a), max_i = (b); i < max_i; i++)
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define fi first
#define se second
#define int long long
using namespace std;
using ll = long long;
using II = pair<int, int>; using VII = vector<II>; using VVII = vector<VII>;
using VI = vector<int>; using VVI = vector<VI>; using VVVI = vector<VVI>;
template <class T = int> inline bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; }
template <class T = int> inline bool chmin(T &a, const T &b) { if (a > b) { a = b; return true; } return false; }
template <class T> ostream& operator<<(ostream &s, const vector<T>& d) { REP (i, d.size()) s << d[i] << (i == d.size() - 1 ? "" : " "); return s; }
template <class T> ostream& operator<<(ostream &s, const vector<vector<T>>& d) { REP (i, d.size()) s << d[i] << (i == d.size() - 1 ? "" : "\n"); return s; }
template <class T, class S> ostream& operator<<(ostream &s, const pair<T, S>& p) { s << "{" << p.first << ", " << p.second << "}"; return s; }
template <class T, class S> ostream& operator<<(ostream& s, const map<T, S> m) { for (auto it = m.begin(); it != m.end(); it++) { s << *it << (next(it) == m.end() ? "" : "\n"); } return s; }
#ifdef _MY_DEBUG
  #define dump(...) cerr << "/* " << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]" << endl, dump_func(__VA_ARGS__), cerr << "*/\n\n";
#else
  #define dump(...)
#endif
void dump_func() { cerr << endl; }
template <class Head, class... Tail> void dump_func(Head&& h, Tail&&... t) { cerr << h << (sizeof...(Tail) == 0 ? "" : ", "), dump_func(forward<Tail>(t)...); }
struct Fast { Fast() { cin.tie(0); ios::sync_with_stdio(false); } } fast;
constexpr int MOD = 1e9 + 7;

using VB = vector<bitset<40>>;
VB rm_nei(const VB& g, int v) {
  int n = g.size();
  VB ret;
  int i0 = 0;
  REP (i, n) {
    if (i == v || g[v][i]) continue;
    ret.push_back(0);
    int j0 = 0;
    REP (j, n) {
      if (j == v || g[v][j]) continue;
      ret[i0][j0] = g[i][j];
      j0++;
    }
    i0++;
  }
  return ret;
}
int solve(VB& g) {
  int n = g.size();
  if (n == 0) return 0;
  int mi = 1e18;
  int v = -1;
  REP (i, n) {
    int deg = g[i].count();
    if (deg < mi) {
      mi = deg;
      v = i;
    }
  }
  VI cans = {v};
  REP (i, n) {
    if (g[v][i]) cans.push_back(i);
  }
  int ans = 0;
  for (int i: cans) {
    VB new_g = rm_nei(g, i);
    ans = max(ans, 1 + solve(new_g));
  }
  return ans;
}
signed main() {
  int n, m; cin >> n >> m;
  VB g(n);
  REP (i, m) {
    int a, b; cin >> a >> b;
    a--;
    b--;
    g[a][b] = 1;
    g[b][a] = 1;
  }
  cout << solve(g) << endl;
}

Submission Info

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