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Submission #367403

# Submission time Handle Problem Language Result Execution time Memory
367403 2021-02-17T07:38:56 Z dolphingarlic Mousetrap (CEOI17_mousetrap) C++14
100 / 100
 1016 ms 183508 KB 
#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

int n, t, m, c;
vector<int> graph[1000001], chain;
ll dp[1000001], pref[1000001];
bool in_chain[1000001];

bool dfs(int node = t, int parent = 0) {
    ll mx1 = 0, mx2 = 0;
    for (int i : graph[node]) if (i != parent) {
        in_chain[node] |= dfs(i, node);
        if (dp[i] >= mx1) mx2 = mx1, mx1 = dp[i];
        else if (dp[i] > mx2) mx2 = dp[i];
    }
    sort(graph[node].begin(), graph[node].end(), [](int A, int B) { return dp[A] > dp[B]; });
    dp[node] = graph[node].size() - 1 + mx2;
    if (in_chain[node]) chain.push_back(node);
    return in_chain[node];
}

bool check(int mn) {
    int rem = 1, used = 0;
    for (int i = c - 1; i; i--, rem++) {
        int allowed = mn - pref[i] - used;
        for (int j : graph[chain[i]]) if (!in_chain[j]) {
            if (dp[j] <= allowed) break;
            if (!rem) return false;
            rem--, used++;
        }
    }
    return true;
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin >> n >> t >> m;
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }
    in_chain[m] = true;
    dfs();
    reverse(chain.begin(), chain.end());
    c = chain.size();
    for (int i = 1; i < c; i++)
        pref[i] = pref[i - 1] + graph[chain[i]].size() - 2 + (i == c - 1);

    int l = pref[c - 1], r = n - 1;
    while (l != r) {
        int mid = (l + r) / 2;
        if (check(mid)) r = mid;
        else l = mid + 1;
    }
    cout << l;
    return 0;
}

Subtask #1
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 15 ms 23788 KB Output is correct
2 Correct 15 ms 23788 KB Output is correct
3 Correct 15 ms 23788 KB Output is correct
4 Correct 15 ms 23788 KB Output is correct
5 Correct 15 ms 23788 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 18 ms 23788 KB Output is correct
9 Correct 17 ms 23788 KB Output is correct
10 Correct 16 ms 23788 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 348 ms 63560 KB Output is correct
2 Correct 318 ms 71532 KB Output is correct
3 Correct 975 ms 78448 KB Output is correct
4 Correct 448 ms 50852 KB Output is correct
5 Correct 943 ms 78444 KB Output is correct
6 Correct 936 ms 78572 KB Output is correct

Subtask #3
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 15 ms 23788 KB Output is correct
2 Correct 15 ms 23788 KB Output is correct
3 Correct 15 ms 23788 KB Output is correct
4 Correct 15 ms 23788 KB Output is correct
5 Correct 15 ms 23788 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 18 ms 23788 KB Output is correct
9 Correct 17 ms 23788 KB Output is correct
10 Correct 16 ms 23788 KB Output is correct
11 Correct 15 ms 23788 KB Output is correct
12 Correct 16 ms 23916 KB Output is correct
13 Correct 16 ms 23916 KB Output is correct
14 Correct 16 ms 24044 KB Output is correct
15 Correct 15 ms 24044 KB Output is correct
16 Correct 15 ms 23916 KB Output is correct
17 Correct 15 ms 23916 KB Output is correct
18 Correct 16 ms 23916 KB Output is correct
19 Correct 15 ms 23916 KB Output is correct
20 Correct 16 ms 23916 KB Output is correct
21 Correct 15 ms 23916 KB Output is correct
22 Correct 16 ms 23916 KB Output is correct

Subtask #4
35.0 / 35.0

# Verdict Execution time Memory Grader output
1 Correct 15 ms 23788 KB Output is correct
2 Correct 15 ms 23788 KB Output is correct
3 Correct 15 ms 23788 KB Output is correct
4 Correct 15 ms 23788 KB Output is correct
5 Correct 15 ms 23788 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 18 ms 23788 KB Output is correct
9 Correct 17 ms 23788 KB Output is correct
10 Correct 16 ms 23788 KB Output is correct
11 Correct 348 ms 63560 KB Output is correct
12 Correct 318 ms 71532 KB Output is correct
13 Correct 975 ms 78448 KB Output is correct
14 Correct 448 ms 50852 KB Output is correct
15 Correct 943 ms 78444 KB Output is correct
16 Correct 936 ms 78572 KB Output is correct
17 Correct 15 ms 23788 KB Output is correct
18 Correct 16 ms 23916 KB Output is correct
19 Correct 16 ms 23916 KB Output is correct
20 Correct 16 ms 24044 KB Output is correct
21 Correct 15 ms 24044 KB Output is correct
22 Correct 15 ms 23916 KB Output is correct
23 Correct 15 ms 23916 KB Output is correct
24 Correct 16 ms 23916 KB Output is correct
25 Correct 15 ms 23916 KB Output is correct
26 Correct 16 ms 23916 KB Output is correct
27 Correct 15 ms 23916 KB Output is correct
28 Correct 16 ms 23916 KB Output is correct
29 Correct 15 ms 23820 KB Output is correct
30 Correct 386 ms 76908 KB Output is correct
31 Correct 365 ms 77032 KB Output is correct
32 Correct 510 ms 183508 KB Output is correct
33 Correct 427 ms 171432 KB Output is correct
34 Correct 923 ms 78404 KB Output is correct
35 Correct 928 ms 78316 KB Output is correct
36 Correct 1008 ms 88848 KB Output is correct
37 Correct 1016 ms 89068 KB Output is correct
38 Correct 824 ms 90980 KB Output is correct
39 Correct 838 ms 90984 KB Output is correct
40 Correct 842 ms 91188 KB Output is correct