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Submission #583485

# Submission time Handle Problem Language Result Execution time Memory
583485 2022-06-25T12:11:12 Z 600Mihnea Mousetrap (CEOI17_mousetrap) C++17
100 / 100
 1113 ms 202668 KB 
#include <bits/stdc++.h>

using namespace std;

const int N = (int) 1e6 + 7;
int n, tr, mo;
vector<int> g[N];
int par[N], cost[N];
bool vis[N];

void build_tree(int a, int p = -1) {
  {
    vector<int> Kids;
    for (auto &b : g[a]) {
      if (b != p) {
        Kids.push_back(b);
      }
    }
    g[a] = Kids;
  }
  for (auto &b : g[a]) {
    build_tree(b, a);
  }
  par[a] = p;
}

void build_cost(int a) {
  if (!vis[a] && a != mo) {
    cost[a] += (int) g[a].size();
  }
  for (auto &b : g[a]) {
    cost[b] += cost[a];
    build_cost(b);
  }
}

void dfs(int a) {
  for (auto &b : g[a]) {
    dfs(b);
  }
  if ((int) g[a].size() == 0) {
    return;
  }
  if ((int) g[a].size() == 1) {
    return;
  }
  assert((int) g[a].size() >= 2);
  vector<int> Values;
  for (auto &b : g[a]) {
    Values.push_back(cost[b]);
  }
  sort(Values.rbegin(), Values.rend());
  assert((int) Values.size() >= 2);
  cost[a] = Values[1];
}

bool ok(int limit) {
  vector<pair<int, int>> guys;
  int dist = 1;
  guys.push_back({0, cost[mo]});
  int v = mo;
  int sum = 0;
  {
    for (int i = 1; i <= n; i++) {
      if ((vis[i] && i != tr) || i == mo) {
        sum += (int) g[i].size() - 1;
      }
    }
    sum++;

  }
  if (sum > limit) {
    return 0;
  }
  int cnt = 0;
  while (v != tr) {
    int skip = 0;
    for (auto &oth : g[v]) {
      if (!vis[oth] && oth != mo) {
        //cout << sum + cost[oth] << " vs " << limit << "\n";
        skip += (sum + cost[oth] <= limit);
        cnt += (sum + cost[oth] > limit);
      }
    }
    sum -= skip;
    if (cnt > dist) return 0;
    v = par[v];
    dist++;
  }
  return 1;
}

signed main() {
  ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

///  freopen ("input.txt", "r", stdin);

  cin >> n >> tr >> mo;

  for (int i = 1; i < n; i++) {
    int a, b;
    cin >> a >> b;
    g[a].push_back(b);
    g[b].push_back(a);
  }
  build_tree(tr);
  {
    int current = par[mo];
    while (current != tr) {
      vis[current] = 1;
      current = par[current];
    }
    vis[current] = 1;
  }
  build_cost(tr);
  dfs(tr);



  int low = 0, high = (int) 1e9 + 7, sol = -1;

  while (low <= high) {
    int mid = (low + high) / 2;
    if (ok(mid)) {
      sol = mid;
      high = mid - 1;
    } else {
      low = mid + 1;
    }
  }

  assert(sol != -1);

  cout << sol << "\n";

}

Subtask #1
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 12 ms 23724 KB Output is correct
2 Correct 12 ms 23764 KB Output is correct
3 Correct 12 ms 23764 KB Output is correct
4 Correct 12 ms 23764 KB Output is correct
5 Correct 12 ms 23764 KB Output is correct
6 Correct 12 ms 23828 KB Output is correct
7 Correct 12 ms 23764 KB Output is correct
8 Correct 13 ms 23704 KB Output is correct
9 Correct 12 ms 23764 KB Output is correct
10 Correct 14 ms 23764 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 387 ms 62824 KB Output is correct
2 Correct 340 ms 58948 KB Output is correct
3 Correct 1000 ms 64032 KB Output is correct
4 Correct 490 ms 43928 KB Output is correct
5 Correct 964 ms 64028 KB Output is correct
6 Correct 982 ms 64032 KB Output is correct

Subtask #3
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 12 ms 23724 KB Output is correct
2 Correct 12 ms 23764 KB Output is correct
3 Correct 12 ms 23764 KB Output is correct
4 Correct 12 ms 23764 KB Output is correct
5 Correct 12 ms 23764 KB Output is correct
6 Correct 12 ms 23828 KB Output is correct
7 Correct 12 ms 23764 KB Output is correct
8 Correct 13 ms 23704 KB Output is correct
9 Correct 12 ms 23764 KB Output is correct
10 Correct 14 ms 23764 KB Output is correct
11 Correct 13 ms 23764 KB Output is correct
12 Correct 12 ms 23772 KB Output is correct
13 Correct 12 ms 23892 KB Output is correct
14 Correct 12 ms 23892 KB Output is correct
15 Correct 13 ms 23904 KB Output is correct
16 Correct 13 ms 23764 KB Output is correct
17 Correct 14 ms 23764 KB Output is correct
18 Correct 13 ms 23852 KB Output is correct
19 Correct 16 ms 23852 KB Output is correct
20 Correct 14 ms 23824 KB Output is correct
21 Correct 13 ms 23948 KB Output is correct
22 Correct 13 ms 23764 KB Output is correct

Subtask #4
35.0 / 35.0

# Verdict Execution time Memory Grader output
1 Correct 12 ms 23724 KB Output is correct
2 Correct 12 ms 23764 KB Output is correct
3 Correct 12 ms 23764 KB Output is correct
4 Correct 12 ms 23764 KB Output is correct
5 Correct 12 ms 23764 KB Output is correct
6 Correct 12 ms 23828 KB Output is correct
7 Correct 12 ms 23764 KB Output is correct
8 Correct 13 ms 23704 KB Output is correct
9 Correct 12 ms 23764 KB Output is correct
10 Correct 14 ms 23764 KB Output is correct
11 Correct 387 ms 62824 KB Output is correct
12 Correct 340 ms 58948 KB Output is correct
13 Correct 1000 ms 64032 KB Output is correct
14 Correct 490 ms 43928 KB Output is correct
15 Correct 964 ms 64028 KB Output is correct
16 Correct 982 ms 64032 KB Output is correct
17 Correct 13 ms 23764 KB Output is correct
18 Correct 12 ms 23772 KB Output is correct
19 Correct 12 ms 23892 KB Output is correct
20 Correct 12 ms 23892 KB Output is correct
21 Correct 13 ms 23904 KB Output is correct
22 Correct 13 ms 23764 KB Output is correct
23 Correct 14 ms 23764 KB Output is correct
24 Correct 13 ms 23852 KB Output is correct
25 Correct 16 ms 23852 KB Output is correct
26 Correct 14 ms 23824 KB Output is correct
27 Correct 13 ms 23948 KB Output is correct
28 Correct 13 ms 23764 KB Output is correct
29 Correct 13 ms 23764 KB Output is correct
30 Correct 402 ms 76276 KB Output is correct
31 Correct 385 ms 76240 KB Output is correct
32 Correct 557 ms 202668 KB Output is correct
33 Correct 440 ms 201840 KB Output is correct
34 Correct 988 ms 77268 KB Output is correct
35 Correct 1016 ms 77308 KB Output is correct
36 Correct 1104 ms 89816 KB Output is correct
37 Correct 1113 ms 89856 KB Output is correct
38 Correct 725 ms 92692 KB Output is correct
39 Correct 747 ms 92740 KB Output is correct
40 Correct 752 ms 92676 KB Output is correct