Submission #1089048

#	Time	Username	Problem	Language	Result	Execution time	Memory
1089048		VMaksimoski008	The Xana coup (BOI21_xanadu)	C++17	100 / 100	127 ms	16980 KiB

xanadu

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

const int maxn = 1e5 + 5;

vector<int> graph[maxn];
int n, vec[maxn], dp[maxn][2][2];

void dfs(int u, int p) {
    dp[u][vec[u]][0] = 0;
    dp[u][vec[u]^1][1] = 1;

    for(int &v : graph[u]) {
        if(v == p) continue;
        dfs(v, u);

        int tmp[2][2];
        tmp[0][0] = tmp[0][1] = tmp[1][0] = tmp[1][1] = 1e9;

        for(int i=0; i<2; i++)
            for(int j=0; j<2; j++)
                for(int k=0; k<2; k++) tmp[i^j][k] = min(tmp[i^j][k], dp[u][i][k] + dp[v][k][j]);

        for(int i=0; i<2; i++)
            for(int j=0; j<2; j++) dp[u][i][j] = tmp[i][j];
    }
}

int main() {
    cin >> n;

    for(int i=0; i<n-1; i++) {
        int a, b; cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    for(int i=1; i<=n; i++) cin >> vec[i];
    for(int i=1; i<=n; i++) dp[i][0][0] = dp[i][0][1] = dp[i][1][0] = dp[i][1][1] = 1e9;
    dfs(1, 1);
    int x = min(dp[1][0][0], dp[1][0][1]);
    if(x == 1e9) cout << "impossible";
    else cout << x;
    return 0;
}

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