Submission #830095

#	Time	Username	Problem	Language	Result	Execution time	Memory
830095		t6twotwo	Mousetrap (CEOI17_mousetrap)	C++17	0 / 100	260 ms	88228 KiB

mousetrap

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N, t, m;
    cin >> N >> t >> m;
    t--, m--;
    vector<vector<int>> adj(N);
    for (int i = 0; i < N - 1; i++) {
        int x, y;
        cin >> x >> y;
        x--, y--;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    vector<int> p(N, -1);
    queue<int> q;
    p[m] = m;
    q.push(m);
    while (!q.empty()) {
        int x = q.front();
        q.pop();
        for (int y : adj[x]) {
            if (p[y] == -1) {
                p[y] = x;
                q.push(y);
            }
        }
    }
    vector<int> path{t};
    while (path.back() != m) {
        path.push_back(p[path.back()]);
    }
    vector<bool> in(N);
    for (int x : path) {
        in[x] = 1;
    }
    vector<int> f(N);
    auto dfs = [&](auto dfs, int x, int p) -> void {
        vector<int> s;
        for (int y : adj[x]) {
            if (y == p || in[y]) {
                continue;
            }
            dfs(dfs, y, x);
            s.push_back(f[y]);
        }
        sort(s.rbegin(), s.rend());
        if (s.empty()) {
            return;
        }
        if (s.size() == 1) {
            f[x] = 1;
            return;
        }
        f[x] = s[1] + s.size();
    };
    vector<vector<int>> ch(N);
    for (int x : path) {
        for (int y : adj[x]) {
            if (!in[y]) {
                ch[x].push_back(y);
            }
        }
        dfs(dfs, x, -1);
    }
    int M = path.size();
    vector<int> z(M + 1);
    for (int i = 0; i < M; i++) {
        z[i + 1] = z[i] + ch[path[i]].size();
    }
    vector<int> dp(M, 1E9);
    dp[1] = f[path[1]];
    for (int i = 2; i < M; i++) {
        vector<int> s;
        for (int j : ch[path[i]]) {
            s.push_back(f[j]);
        }
        sort(s.rbegin(), s.rend());
        if (s.empty()) {
            dp[i] = max(0, dp[i - 1] - 1);
        } else {
            dp[i] = max({0, dp[i - 1] - 1, s[0] + z[i + 1]});
            if (s.size() == 1) {
                dp[i] = min(dp[i], dp[i - 1] + 1);
            } else {
                dp[i] = min(dp[i], max(dp[i - 1] + 1, s[1] + z[i + 1]));
            }
        }
    }
    for (int i = 1; i < M; i++) {
        cout << path[i] + 1 << " " << z[i + 1] << " " << dp[i] << "\n";
    }
    cout << dp[M - 1] << "\n";
    return 6/22;
}

• Subtask 1: 0 / 20
• Subtask 2: 0 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35