Submission #465275

#	Time	Username	Problem	Language	Result	Execution time	Memory
465275		AmShZ	The Xana coup (BOI21_xanadu)	C++11	100 / 100	81 ms	18404 KiB

xanadu

//khodaya khodet komak kon
# include <bits/stdc++.h>

using namespace std;

typedef long long                                        ll;
typedef long double                                      ld;
typedef pair <int, int>                                  pii;
typedef pair <pii, int>                                  ppi;
typedef pair <int, pii>                                  pip;
typedef pair <pii, pii>                                  ppp;
typedef pair <ll, ll>                                    pll;

# define A                                               first
# define B                                               second
# define endl                                            '\n'
# define sep                                             ' '
# define all(x)                                          x.begin(), x.end()
# define kill(x)                                         return cout << x << endl, 0
# define SZ(x)                                           int(x.size())
# define lc                                              id << 1
# define rc                                              id << 1 | 1
# define fast_io                                         ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);

ll power(ll a, ll b, ll md) {return (!b ? 1 : (b & 1 ? a * power(a * a % md, b / 2, md) % md : power(a * a % md, b / 2, md) % md));}

const int xn = 1e5 + 10;
const int xm = - 20 + 10;
const int sq = 320;
const int inf = 1e9 + 10;
const ll INF = 1e18 + 10;
const ld eps = 1e-15;
const int mod = 1e9 + 7;//998244353;
const int base = 257;

int n, dp[xn][2][2], pd[2][2], ans = inf, f[xn];
vector <int> adj[xn];

void DFS(int v, int p = - 1){
	dp[v][0][1] = dp[v][1][1] = inf;
	dp[v][0][0] = 0, dp[v][1][0] = 1;
	for (int u : adj[v]){
		if (u == p)
			continue;
		DFS(u, v);
		for (int i = 0; i < 2; ++ i)
			for (int j = 0; j < 2; ++ j)
				pd[i][j] = dp[v][i][j], dp[v][i][j] = inf;
		for (int f1 = 0; f1 < 2; ++ f1)
			for (int f2 = 0; f2 < 2; ++ f2)
				for (int f3 = 0; f3 < 2; ++ f3)
					for (int f4 = 0; f4 < 2; ++ f4)
						if ((f1 ^ f3 ^ f4) == f[u])
							dp[v][f1][f2 ^ f3] = min(dp[v][f1][f2 ^ f3], pd[f1][f2] + dp[u][f3][f4]);
	}
}

int main(){
	fast_io;

	cin >> n;
	for (int i = 1; i < n; ++ i){
		int v, u;
		cin >> v >> u;
		adj[v].push_back(u);
		adj[u].push_back(v);
	}
	for (int i = 1; i <= n; ++ i)
		cin >> f[i];
	DFS(1);
	for (int i = 0; i < 2; ++ i)
		for (int j = 0; j < 2; ++ j)
			if ((i ^ j) == f[1])
				ans = min(ans, dp[1][i][j]);
	if (ans == inf)
		kill("impossible");
	cout << ans << endl;

	return 0;
}

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