Submission #469144

#	Time	Username	Problem	Language	Result	Execution time	Memory
469144		ivan_tudor	Mousetrap (CEOI17_mousetrap)	C++14	45 / 100	985 ms	67940 KiB

mousetrap

#include<bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5;
int dp[N];
int h[N];
bool viz[N];
vector<int> gr[N];
int par[N];
void first_dfs(int nod, int dad){
  par[nod] = dad;
  h[nod] = 1 + h[dad];
  for(auto x:gr[nod]){
    if(x != dad)
      first_dfs(x, nod);
  }
}
void dfs(int nod, int dad){
  int nrvec = 0;
  for(auto x:gr[nod]){
    if(x == dad || viz[x] == true)
      continue;
    nrvec++;
    dfs(x, nod);
  }
  if(nrvec == 1){
    dp[nod] = 1;
    return;
  }
  int m1 = 0, m2 = 0;
  for(auto x:gr[nod]){
    if(x == dad || viz[x])
      continue;
    if(nrvec + dp[x] > m1){
      m2 = m1;
      m1 = nrvec +  dp[x];
    }
    else if(nrvec +  dp[x] > m2){
      m2 = nrvec +  dp[x];
    }
  }
  dp[nod] = m2;
}
int ans = 0;
int sm[N];
set<pair<pair<int, int>, int>> ms;
int solve(int nod){
  viz[nod] = true;
  if(par[nod] == 0)
    return 0;
  int sum = solve(par[nod]);
  dfs(nod, 0);
  ms.insert({{sum + dp[nod], h[nod]}, nod});
  sm[nod] = sum + dp[nod];
  sum += gr[nod].size() - (par[nod] != 0) - 1;
  return sum;
}
void solvefr(int nod){
  if(par[nod] == 0)
    return;
  ans = max(ans, sm[nod]);
  ms.erase({{sm[nod], h[nod]}, nod});
  if(ms.size()){
    int id = (*ms.rbegin()).second;
    ms.erase(*ms.rbegin());
    sm[id] --;
    ms.insert({{sm[id], h[id]}, id});
  }
}
int main()
{
  //freopen(".in","r",stdin);
  ios::sync_with_stdio(false);
  cin.tie(0),cout.tie(0);
  int n, root, m;
  cin>>n>>root>>m;
  for(int i =1 ; i<n; i++){
    int x, y;
    cin>>x>>y;
    gr[x].push_back(y);
    gr[y].push_back(x);
  }
  first_dfs(root, 0);
  solve(m);
  solvefr(m);
  cout<<ans;
  return 0;
}

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