제출 #873905

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
873905		noiaint	The Xana coup (BOI21_xanadu)	C++17	100 / 100	68 ms	42992 KiB

xanadu

#include <bits/stdc++.h>

using namespace std;

#define file ""

#define mp make_pair
#define fi first
#define se second
#define all(x) x.begin(), x.end()

#define getbit(x, i) (((x) >> (i)) & 1)
#define bit(x) (1LL << (x))
#define popcount __builtin_popcountll

mt19937_64 rd(chrono::steady_clock::now().time_since_epoch().count());
int rand(int l, int r) {
    return l + rd() % (r - l + 1);
}

const int N = 1e6 + 5;
const int mod = (int)1e9 + 7; // 998244353;
const int lg = 25; // lg + 1
const int oo = 1e9;
const long long ooo = 1e18;

template<class X, class Y> bool mini(X &a, Y b) {
    return a > b ? (a = b, true) : false;
}
template<class X, class Y> bool maxi(X &a, Y b) {
    return a < b ? (a = b, true) : false;
}
void add(int &a, int b) {
    a += b;
    if (a >= mod) a -= mod;
    if (a < 0) a += mod;
}

int n;
vector<int> adj[N];
int state[N];

int f[N][2][2];

/*
f[u][i][j] : minimum number of moves to turn off subtree u
i = 0/1 if we toggle p
j = 0/1 if we toggle u
*/

void dfs(int u, int p) {
    for (int i = 0; i < 2; ++i) {
        f[u][i][state[u] ^ i] = i;
        f[u][i][state[u] ^ i ^ 1] = oo;
    }

    for (int v : adj[u]) if (v != p) {
        dfs(v, u);

        for (int i = 0; i < 2; ++i) {
            int even = f[u][i][0];
            int odd = f[u][i][1];
            
            f[u][i][0] = min({oo, even + f[v][0][i], odd + f[v][1][i]});
            f[u][i][1] = min({oo, even + f[v][1][i], odd + f[v][0][i]});
        }

    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    // freopen(file".inp", "r", stdin);
    // freopen(file".out", "w", stdout);

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

    dfs(1, 0);

    int ans = min(f[1][0][0], f[1][1][0]);
    if (ans == oo) return cout << "impossible", 0;
    cout << ans;

    return 0;
}

/*

*/

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