Submission #702890

#	Time	Username	Problem	Language	Result	Execution time	Memory
702890		sdfsf	Mousetrap (CEOI17_mousetrap)	C++11	25 / 100	918 ms	113832 KiB

mousetrap

#include "bits/stdc++.h"
using namespace std;
#define int long long
const int N = 1e6 + 50;
const long long INF = 1ll << 60;
int F[N], n, t, m, ch[N], pr[N], bala[N], A[N], h[N];
vector<int> adj[N];

void dfs2(int v, int p) {
    for (auto u: adj[v]) if (u != p) {
        bala[u] = bala[v] + ch[v] - 1;
        dfs2(u, v);
    }
}

void dfs(int v, int p) {
    pr[v] = p;
    vector<int> tmp;
    for (auto u: adj[v]) if (u != p) {
        h[u] = h[v] + 1;
        dfs(u, v);
        tmp.push_back(F[u]);
        ch[v]++;
    }
    sort(tmp.rbegin(), tmp.rend());
    if (tmp.size() <= 1)
        F[v] = tmp.size();
    else
        F[v] = tmp[1] + tmp.size();
}

bool is_valid() {
    int s = 0;
    for (int i = 0; i <= n; i++) {
        s += A[i];
        if (s > i + 1) {
            return false;
        }
    }
    return true;
}

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> t >> m;
    t--, m--;
    for (int i = 1; i < n; i++) {
        int u, v; cin >> u >> v; u--, v--;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    if (m == t) {
        cout << 0 << '\n';
        return 0;
    }
    dfs(t, t);
    ch[t] = 1;
    dfs2(t, t);
    vector<pair<int, int>> X;
    int tmp_m = m;
    int child = -1;
    int co = 0;
    while (m != t) {
        for (auto u: adj[m]) if (u != pr[m] && u != child) {
            if (m == tmp_m) 
                X.emplace_back(F[u] + 1 + bala[u], u); 
            else
                X.emplace_back(F[u] + 1 + bala[u] - 1, u);
        }
        child = m;
        m = pr[m];
        assert(co++ <= n);
    }
    sort(X.rbegin(), X.rend());

    for (auto p: X) {
        int f = p.first;
        int u = p.second;
        assert(h[tmp_m] - h[u] + 1 >= 0);
        A[h[tmp_m] - h[u] + 1]++;
        if (!is_valid()) {
            cout << f << '\n';
            return 0;
        }
    }
    cout << 0 << '\n';
    return 0;
}

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