Submission #3635448

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Source Code Expand

#include "bits/stdc++.h"

using namespace std;
using ll = long long;
using ull = unsigned long long;

typedef pair< int, int > Pi;
typedef pair< long long, long long > P;
typedef pair< long long, P > PP;
typedef pair< P, P > PPP;

const double DINF = 5e14, eps = 1e-10;
const long long MOD = 1e9 + 7, INF = 5e18;
const int di[4] = { 1,0,-1,0 }, dj[4] = { 0,1,0,-1 };

#define fr first
#define sc second
#define pb push_back
#define eb emplace_back
#define ALL(x) (x).begin(),(x).end()

int n,m,a,b;
bool r[710][710];
int cl[710],vi[710];
bool dp[710][710];
vector<int>cg[710];
vector<P>v;

P dfs(int now,int color){
	vi[now]=1;
	cl[now]=color;
	P ret=P(0,0);
	if(color==1)ret.fr++;
	else ret.sc++;
	for(int u:cg[now]){
		if(vi[u]&&cl[u]==cl[now])return P(-1,-1);
		else if(!vi[u]){
			int c;
			if(color==1)c=2;
			else c=1;
			P p=dfs(u,c);
			if(p.fr<0)return P(-1,-1);
			ret.fr+=p.fr;
			ret.sc+=p.sc;
		} 
	}
	return ret;
}

void set_up(){
	cin>>n>>m;
	for(int i=0;i<m;i++){
		cin>>a>>b;
		a--,b--;
		r[a][b]=true;
		r[b][a]=true;
	}	
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
			if(!r[i][j]&&i!=j)cg[i].eb(j);
		}
	}
}

void solve(){
	for(int i=0;i<n;i++){
		if(vi[i])continue;
		P p=dfs(i,1);
		if(p.fr==-1){
			cout<<-1<<endl;
			return;
		}
		v.eb(p);
	}
	int ans=1e9;
	dp[0][0]=true;
	for(int i=0;i<v.size();i++){
		for(int j=0;j<n;j++){
			if(dp[i][j]){
				dp[i+1][j+v[i].fr]=true;
				dp[i+1][j+v[i].sc]=true;
			}
		}
	}
	for(int i=0;i<n;i++){
		if(dp[v.size()][i])ans=min(ans,i*(i-1)/2+(n-i)*(n-i-1)/2);
	}
	cout<<ans<<endl;
}

int main() {
	set_up();
	solve();
	return 0;
}

Submission Info

Judge Result