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Submission #844789

# Submission time Handle Problem Language Result Execution time Memory
844789 2023-09-06T00:23:27 Z treewave Mousetrap (CEOI17_mousetrap) C++17
100 / 100
 1052 ms 276264 KB 
#include <bits/stdc++.h>

using namespace std;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n, t, m; cin >> n >> t >> m; t--; m--;
    vector<vector<int>> adj(n);
    for (int i = 0; i < n-1; i++){
        int a, b; cin >> a >> b; a--; b--;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }

    vector<vector<int>> children(n);
    vector<int> moves_above(n);
    vector<int> dp(n);
    vector<int> path_to_m;

//    cerr << "hi" << endl;

    auto dfs_init = [&](auto self, int u, int v) -> bool{
        bool m_in_subtree = false;
        if (u == m) m_in_subtree = true;
        for (int neighbor : adj[u]){
            if (neighbor != v){
                children[u].push_back(neighbor);
                m_in_subtree |= self(self, neighbor, u);
            }
        }
        if (m_in_subtree){
            path_to_m.push_back(u);
        }
        return m_in_subtree;
    };

    dfs_init(dfs_init, t, -1);

//    cerr << "dfs_init" << endl;

    auto dfs_actual = [&](auto self, int u, int ma) -> void{
        moves_above[u] = ma;
        if (u != t){
            ma += children[u].size() - 1;
        }

        vector<int> children_dp;
        for (int neighbor : children[u]){
            self(self, neighbor, ma);
            children_dp.push_back(dp[neighbor]);
        }
        sort(children_dp.begin(), children_dp.end());
        if (children_dp.empty()){
            dp[u] = 0;
        }
        else if (children_dp.size() == 1){
            dp[u] = 1;
        }
        else{
            dp[u] = children_dp[children_dp.size() - 2] + children_dp.size() - 1 + 1;
        }
    };

    dfs_actual(dfs_actual, t, 0);

//    cerr << "dfs_actual" << endl;

    auto ok = [&](int mid){
        int free = 0; //number of restrictions can place
        for (int i = 0; i < path_to_m.size() - 1; i++){
            free++;
            int node = path_to_m[i];
            vector<int> children_dp;
            for (int child : children[node]){
                if (i == 0){
                    children_dp.push_back(dp[child] + children[node].size() - 1 + moves_above[node] + 1);
                }
                else{
                    if (child != path_to_m[i-1]){
                        children_dp.push_back(dp[child] + children[node].size() - 2 + moves_above[node] + 1);
                    }
                }
            }
            if (children_dp.size() == 0){}
            else{
                sort(children_dp.begin(), children_dp.end());
                int sub_from_mid = 0;
                while (children_dp.size() && children_dp.back() > mid){
                    children_dp.pop_back(); free--; sub_from_mid++;
                    if (free < 0) return false;
                }
                mid -= sub_from_mid;
            }
            if (free < 0) return false;
        }
        if (mid < 0) return false;
        return true;
    };

    int lo = 0, hi = 1e9;
    while (lo < hi){
        int mid = (lo + hi) / 2;
        if (ok(mid)){
            hi = mid;
        }
        else{
            lo = mid + 1;
        }
    }
    cout << lo << "\n";
}

Compilation message

mousetrap.cpp: In lambda function:
mousetrap.cpp:72:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   72 |         for (int i = 0; i < path_to_m.size() - 1; i++){
      |                         ~~^~~~~~~~~~~~~~~~~~~~~~

Subtask #1
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 348 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 0 ms 348 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 272 ms 102008 KB Output is correct
2 Correct 246 ms 91840 KB Output is correct
3 Correct 779 ms 103812 KB Output is correct
4 Correct 321 ms 52564 KB Output is correct
5 Correct 762 ms 103896 KB Output is correct
6 Correct 758 ms 103848 KB Output is correct

Subtask #3
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 348 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 0 ms 348 KB Output is correct
11 Correct 0 ms 344 KB Output is correct
12 Correct 1 ms 348 KB Output is correct
13 Correct 1 ms 348 KB Output is correct
14 Correct 1 ms 604 KB Output is correct
15 Correct 1 ms 604 KB Output is correct
16 Correct 1 ms 348 KB Output is correct
17 Correct 1 ms 344 KB Output is correct
18 Correct 1 ms 348 KB Output is correct
19 Correct 1 ms 348 KB Output is correct
20 Correct 1 ms 344 KB Output is correct
21 Correct 1 ms 348 KB Output is correct
22 Correct 1 ms 348 KB Output is correct

Subtask #4
35.0 / 35.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 348 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 0 ms 348 KB Output is correct
11 Correct 272 ms 102008 KB Output is correct
12 Correct 246 ms 91840 KB Output is correct
13 Correct 779 ms 103812 KB Output is correct
14 Correct 321 ms 52564 KB Output is correct
15 Correct 762 ms 103896 KB Output is correct
16 Correct 758 ms 103848 KB Output is correct
17 Correct 0 ms 344 KB Output is correct
18 Correct 1 ms 348 KB Output is correct
19 Correct 1 ms 348 KB Output is correct
20 Correct 1 ms 604 KB Output is correct
21 Correct 1 ms 604 KB Output is correct
22 Correct 1 ms 348 KB Output is correct
23 Correct 1 ms 344 KB Output is correct
24 Correct 1 ms 348 KB Output is correct
25 Correct 1 ms 348 KB Output is correct
26 Correct 1 ms 344 KB Output is correct
27 Correct 1 ms 348 KB Output is correct
28 Correct 1 ms 348 KB Output is correct
29 Correct 0 ms 348 KB Output is correct
30 Correct 272 ms 115528 KB Output is correct
31 Correct 268 ms 115580 KB Output is correct
32 Correct 512 ms 276264 KB Output is correct
33 Correct 373 ms 272208 KB Output is correct
34 Correct 778 ms 117048 KB Output is correct
35 Correct 802 ms 116856 KB Output is correct
36 Correct 1052 ms 131468 KB Output is correct
37 Correct 1000 ms 131524 KB Output is correct
38 Correct 605 ms 126924 KB Output is correct
39 Correct 611 ms 127040 KB Output is correct
40 Correct 617 ms 126880 KB Output is correct