Submission #657587

#	Time	Username	Problem	Language	Result	Execution time	Memory
657587		baojiaopisu	The Xana coup (BOI21_xanadu)	C++14	100 / 100	72 ms	20188 KiB

xanadu

#include<bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using ull = unsigned long long;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;

#define fi first
#define se second
#define left BAO
#define right ANH
#define pb push_back
#define pf push_front
#define mp make_pair
#define ins insert
#define btpc __builtin_popcount
#define btclz __builtin_clz

#define sz(x) (int)(x.size());
#define all(x) x.begin(), x.end()
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};

template<class X, class Y>
    bool minimize(X &x, const Y &y) {
        if (x > y)
        {
            x = y;
            return true;
        }
        return false;
    }
template<class X, class Y>
    bool maximize(X &x, const Y &y) {
        if (x < y)
        {
            x = y;
            return true;
        }
        return false;
    }

const int MOD = 1e9 + 7; //998244353

template<class X, class Y>
	void add(X &x, const Y &y) {
		x = (x + y);
		if(x >= MOD) x -= MOD;
	}

template<class X, class Y> 
	void sub(X &x, const Y &y) {
		x = (x - y);
		if(x < 0) x += MOD;
	}

/* Author : Le Ngoc Bao Anh, 12A5, LQD High School for Gifted Student*/

const ll INF = 1e9;
const int N = 1e5 + 10;

ll dp[N][2][2];
ll f[N][2][2], nf[2][2];
vector<int> adj[N];
int state[N];

void dfs(int u, int par) {
	//f(press, color)
	int child = 0;
	for(int i = 0; i < 2; i++) {
		for(int j = 0; j < 2; j++) {
			f[u][i][j] = dp[u][i][j] = INF;
		}
	}
	f[u][0][0] = f[u][0][1] = 0;

	for(auto v : adj[u]) {
		if(v != par) {
			dfs(v, u);
			child = true;
			for(int i = 0; i < 2; i++) {
				for(int j = 0; j < 2; j++) {
					nf[i][j] = INF;
				}
			}

			for(int j = 0; j < 2; j++) {
				for(int i = 0; i < 2; i++) {
					for(int x = 0; x < 2; x++) {
						minimize(nf[i ^ x][j], f[u][i][j] + dp[v][x][j]);  
					}
				}
			}

			for(int i = 0; i < 2; i++) {
				for(int j = 0; j < 2; j++) {
					f[u][i][j] = nf[i][j];
				}
			}

		}
	}

	if(!child) {
		for(int i = 0; i < 2; i++) {
			dp[u][i][state[u] ^ i] = i;
		}
		return;
	}

	for(int i = 0; i < 2; i++) {
		for(int j = 0; j < 2; j++) {
			minimize(dp[u][j][state[u] ^ i ^ j], f[u][i][j] + j);
		}
	}
}

void BaoJiaoPisu() {
	int n; cin >> n;
	for(int i = 1; i < n; i++) {
		int u, v; cin >> u >> v;
		adj[u].pb(v);
		adj[v].pb(u);
	}

	for(int i = 1; i <= n; i++) cin >> state[i];
	dfs(1, 0);

	ll ans = min(dp[1][0][0], dp[1][1][0]);
	if(ans >= INF) cout << "impossible";
	else cout << ans;
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int tc = 1, ddd = 0;
    // cin >> tc;
    while(tc--) {
        //ddd++;
        //cout << "Case #" << ddd << ": ";
        BaoJiaoPisu();
    }
}

Compilation message (stderr)

xanadu.cpp: In function 'int main()':
xanadu.cpp:148:17: warning: unused variable 'ddd' [-Wunused-variable]
  148 |     int tc = 1, ddd = 0;
      |                 ^~~

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