Submission #583432

#	Time	Username	Problem	Language	Result	Execution time	Memory
583432		600Mihnea	Mousetrap (CEOI17_mousetrap)	C++17	25 / 100	1010 ms	64176 KiB

mousetrap

#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];

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) {
  cost[a] += (int) g[a].size() - 1 + 1;
  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];
}

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);
  build_cost(tr);
  dfs(tr);

  cout << cost[mo] - 1 << "\n";


}

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