Submission #398903

#	Time	Username	Problem	Language	Result	Execution time	Memory
398903		AmineWeslati	The Xana coup (BOI21_xanadu)	C++14	55 / 100	133 ms	18660 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<int>vi;
#define pb push_back
#define sz(v) (int)v.size()
#define FOR(i,a,b) for(int i=a; i<b; i++)

void ckmin(int &x, int y){x=min(x,y);}

void IO() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin); 
    freopen("output.txt", "w", stdout);
#endif
}
//------------------------------------------------//

const int MX=1e5+10;
const int INF=1e9;
int N; 
vi adj[MX],a(MX);

int memo[MX][2][2];
int solve(int u, int p, int f, int ff){
	int &ind=memo[u][f][ff];
	if(ind!=-1) return ind; 

	int st=a[u]; if(f) st=1-st; if(ff) st=1-st;

	int ans=INF,n=sz(adj[u])-(u!=1); 
	
	FOR(m,0,((1)<<(n))) if(((__builtin_popcount(m))&1)==st){
		int cur=ff,idx=0;
		for(int v: adj[u]) if(v!=p){
			int nf=(((m)>>(idx))&1);
			cur+=solve(v,u,ff,nf);
			if(cur>INF) cur=INF;
			idx++;
		}
		ckmin(ans,cur);
	}
	
	return ind=ans; 
}

int main(){
	IO();

	cin>>N;
	FOR(i,0,N-1){
		int u,v; cin>>u>>v;
		adj[u].pb(v);
		adj[v].pb(u);
	}
	FOR(i,1,N+1) cin>>a[i];

	memset(memo,-1,sizeof(memo));
	int ans=min(solve(1,1,0,0),solve(1,1,0,1));
	if(ans==INF) cout << "impossible" << endl;
	else cout << ans << endl;

}

• Subtask 1: 5 / 5
• Subtask 2: 0 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 0 / 30