제출 #1293964

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1293964		chill7fo	Paprike (COI18_paprike)	C++20	13 / 100	28 ms	8268 KiB

paprike

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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int n;
    ll k;
    if (!(cin >> n >> k)) return 0;
    vector<ll> b(n+1);
    for (int i = 1; i <= n; ++i) cin >> b[i];
    vector<vector<int>> g(n+1);
    for (int i = 0; i < n-1; ++i) {
        int x, y; cin >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
    }

    if (n == 1) {
        if (b[1] > k) cout << 1 << "\n";
        else cout << 0 << "\n";
        return 0;
    }

    auto farthest_from = [&](int s) {
        vector<int> dist(n+1, -1);
        queue<int> q;
        q.push(s);
        dist[s] = 0;
        int best = s;
        while (!q.empty()) {
            int v = q.front(); q.pop();
            if (dist[v] > dist[best]) best = v;
            for (int u: g[v]) if (dist[u] == -1) {
                dist[u] = dist[v] + 1;
                q.push(u);
            }
        }
        return best;
    };

    int a = farthest_from(1);
    int bnode = farthest_from(a);

    auto solve = [&](int root)->ll {
        vector<int> parent(n+1, 0);
        vector<int> order;
        order.reserve(n);

        vector<int> st;
        st.push_back(root);
        parent[root] = 0;
        while (!st.empty()) {
            int v = st.back(); st.pop_back();
            order.push_back(v);
            for (int u: g[v]) {
                if (u == parent[v]) continue;
                parent[u] = v;
                st.push_back(u);
            }
        }

        vector<ll> sum(n+1, 0);
        for (int i = 1; i <= n; ++i) sum[i] = b[i];
        ll cuts = 0;

        for (int idx = (int)order.size() - 1; idx >= 0; --idx) {
            int v = order[idx];
            if (sum[v] > k) {
                cuts++;
                sum[v] = 0;
            }
            int p = parent[v];
            if (p != 0 && sum[v] > 0) {
                if (sum[p] + sum[v] > k) {
                    cuts++;
                } else {
                    sum[p] += sum[v];
                }
            }
        }
        return cuts;
    };

    ll ans1 = solve(a);
    ll ans2 = solve(bnode);
    ll ans = min(ans1, ans2);
    cout << ans << "\n";
    return 0;
}

• Subtask 1: 0 / 11
• Subtask 2: 13 / 13
• Subtask 3: 0 / 27
• Subtask 4: 0 / 49