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Submission #367399

# Submission time Handle Problem Language Result Execution time Memory
367399 2021-02-17T07:19:43 Z dolphingarlic Mousetrap (CEOI17_mousetrap) C++14
0 / 100
 357 ms 76908 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--, allowed--, 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
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 23804 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 15 ms 23788 KB Output is correct
9 Incorrect 15 ms 23788 KB Output isn't correct
10 Halted 0 ms 0 KB -

Subtask #2
0 / 25.0

# Verdict Execution time Memory Grader output
1 Incorrect 357 ms 76908 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #3
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 23804 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 15 ms 23788 KB Output is correct
9 Incorrect 15 ms 23788 KB Output isn't correct
10 Halted 0 ms 0 KB -

Subtask #4
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 23804 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23788 KB Output is correct
8 Correct 15 ms 23788 KB Output is correct
9 Incorrect 15 ms 23788 KB Output isn't correct
10 Halted 0 ms 0 KB -