Submission #415166

#	Time	Username	Problem	Language	Result	Execution time	Memory
415166		tengiz05	The Xana coup (BOI21_xanadu)	C++17	0 / 100	84 ms	18604 KiB

xanadu

#include <bits/stdc++.h>
using i64 = long long;
constexpr int N = 1e5;
int dp[N][2][2], a[N];
std::vector<int> e[N];
void dfs(int u, int p) {
    if (e[u].size() == 1 && p != -1) {
        if (a[u] == 0) {
            dp[u][0][0] = 0;
            dp[u][1][1] = 1;
        } else {
            dp[u][1][0] = 0;
            dp[u][0][1] = 1;
        }
        return;
    }
    std::vector<int> c;
    for (auto v : e[u]) {
        if (v == p) continue;
        dfs(v, u);
        c.push_back(v);
    }
    int k = c.size();
    if (k == 1) {
        int l = c[0];
        if (a[u] == 0) {
            dp[u][0][0] = dp[l][0][0];
            dp[u][0][1] = dp[l][1][1] + 1;
            dp[u][1][0] = dp[l][0][1];
            dp[u][1][1] = dp[l][1][0] + 1;
        } else {
            dp[u][1][0] = dp[l][1][0];
            dp[u][1][1] = dp[l][1][1] + 1;
            dp[u][0][0] = dp[l][0][1];
            dp[u][0][1] = dp[l][1][0] + 1;
        }
    }
}
int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int n;
    std::cin >> n;
    for (int i = 0; i < n - 1; i++) {
        int u, v;
        std::cin >> u >> v;
        u--;
        v--;
        e[u].push_back(v);
        e[v].push_back(u);
    }
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
    }
    memset(dp, 0x3f, sizeof dp);
    dfs(0, -1);
    int ans = 1e9;
    for (int j = 0; j < 2; j++) {
        ans = std::min(ans, dp[0][0][j]);
    }
    if (ans == 1e9) {
        std::cout << "impossible\n";
    } else {
        std::cout << ans << "\n";
    }
    return 0;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 15
• Subtask 3: 0 / 10
• Subtask 4: 0 / 40
• Subtask 5: 0 / 30