Submission #705863

#	Time	Username	Problem	Language	Result	Execution time	Memory
705863		Chal1shkan	The Xana coup (BOI21_xanadu)	C++14	100 / 100	67 ms	20428 KiB

xanadu

# include <bits/stdc++.h>
 
# define pb push_back
# define ff first
# define ss second
# define nl "\n"
# define sz(x) ((int)(x).size())
# define deb(x) cerr << #x  << " = " << x << endl; 
# define pll pair <ll, ll>
 
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
 
const ll maxn = 1e5 + 25;
const ll inf = 2e9 + 0;
const ll mod = 1e9 + 123;
const ll dx[] = {-1, 1, 0, 0};
const ll dy[] = {0, 0, -1, 1};
 
using namespace std;

ll n, col[maxn];
vector <ll> g[maxn];
ll dp[maxn][2][2];

void dfs (ll v, ll pa)
{
	ll tmp[2][2];
	tmp[0][0] = 0;
	tmp[1][0] = 0;
	tmp[0][1] = inf;
	tmp[1][1] = inf;
	for (ll to : g[v])
	{
		if (to == pa) continue;
		dfs(to, v);
		ll t[2][2];
		t[0][0] = min(tmp[0][1] + dp[to][0][1], tmp[0][0] + dp[to][0][0]);
		t[0][1] = min(tmp[0][0] + dp[to][0][1], tmp[0][1] + dp[to][0][0]);
		t[1][0] = min(tmp[1][1] + dp[to][1][1], tmp[1][0] + dp[to][1][0]);
		t[1][1] = min(tmp[1][0] + dp[to][1][1], tmp[1][1] + dp[to][1][0]);
		for (ll i = 0; i < 2; ++i) 
		{
			for (ll j = 0; j < 2; ++j)
			{
				tmp[i][j] = t[i][j];
			}
		}
	}
	if (col[v])
    {
        dp[v][0][0] = tmp[0][1];
        dp[v][0][1] = 1 + tmp[1][0];
        dp[v][1][0] = tmp[0][0];
        dp[v][1][1] = 1 + tmp[1][1];
    }
    else 
	{
        dp[v][0][0] = tmp[0][0];
        dp[v][0][1] = 1 + tmp[1][1];
        dp[v][1][0] = tmp[0][1];
        dp[v][1][1] = 1 + tmp[1][0];
    }
}

void ma1n (/* SABR */)
{
	cin >> n;
	for (ll i = 1, u, v; i < n; ++i)
	{
		cin >> u >> v;
		g[u].pb(v);
		g[v].pb(u);
	}
	for (ll i = 1; i <= n; ++i)
	{
		cin >> col[i];
	}
	dfs(1, 1);
	ll ans = min({dp[1][0][1], dp[1][0][0]});
	if (ans >= inf) cout << "impossible" << nl;
	else cout << ans << nl;
}
 
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
//  freopen("angry.in", "r", stdin);
// freopen("angry.out", "w", stdout);
    int ttt = 1;
//  cin >> ttt;
    for (int test = 1; test <= ttt; ++test)
    {
//      cout << "Case " << test << ":" << ' ';
        ma1n();
    }
    return 0;
}

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