Submission #18218623

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Source Code Expand

#include <bits/stdc++.h>
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define chmin(x,y) x = min((x),(y));
#define chmax(x,y) x = max((x),(y));
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
const int INF = 1e9;
const long long LINF = 1e17;
const int MOD = 1000000007;
//const int MOD = 998244353;
const double PI = 3.14159265358979323846;

ll dp[(1<<20)+5];
ll ng[50];

int main(){
    ll n,m;
    cin >> n >> m;
    vector<ll> a(m),b(m);
    rep(i,m) cin >> a[i] >> b[i];
    rep(i,m) --a[i],--b[i];
    if(n==1){
        cout << 1 << endl;
        return 0;
    }
    rep(i,n){
        ll mask = 0;
        rep(j,m){
            if(a[j] == i) mask += 1<<b[j];
            else if(b[j] == i) mask += 1<<a[j];
        }
        ng[i] = mask;
    }
    rep(bit,1<<(n/2)){
        bool ok = true;
        rep(i,n/2){
            if(bit>>i&1){
                if((ng[i] & bit) > 0) ok = false;
            }
        }
        if(ok) dp[bit] = __builtin_popcountll(bit);
        else{
            rep(i,n/2){
                if(bit>>i&1) chmax(dp[bit],dp[bit^(1<<i)]);
            }
        }
    }

    ll ans = 0;
    rep(bit,1<<((n+1)/2)){
        bool ok = true;
        rep(i,(n+1)/2){
            if(bit>>i&1){
                if((ng[n/2+i] & (bit<<(n/2))) > 0) ok = false;
            }
        }
        if(ok){
            ll mask = 0;
            rep(i,(n+1)/2){
                if(bit>>i&1) mask |= ng[n/2+i];
            }
            mask &= (1<<(n/2))-1;
            mask ^= (1<<(n/2))-1;
            chmax(ans,dp[mask]+__builtin_popcountll(bit));
        }
    }
    cout << ans << endl;
    return 0;
}

Submission Info

Judge Result