Submission #1067827

#	Time	Username	Problem	Language	Result	Execution time	Memory
1067827		kunzaZa183	Torrent (COI16_torrent)	C++17	31 / 100	692 ms	27220 KiB

torrent

#include <bits/stdc++.h>
using namespace std;
int main(){
  int n,st,ed;
  cin>>n>>st>>ed;
  st--,ed--;

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

  vector<int> bet(n);
  vector<int> path;

  function<void(int,int)> fp = [&](int cur,int par) {
    path.push_back(cur);
    if(cur==ed){
      return;
    }
    for(auto a:adj[cur])
      if(a!=par) {
        fp(a,cur);
        if(path.back()==ed)
          return;
      }
    path.pop_back();
  };
  fp(st,st);

  for(auto a:path)
    bet[a] = 1;

  auto valv = [&](vector<int> & vi) {
    if(vi.empty())
      return 0;
    sort(vi.begin(),vi.end(),greater<int>());
    for(int i = 0; i < vi.size();i++)
      vi[i] += i+1;
    return *max_element(vi.begin(),vi.end());
  };
  
  function<int(int,int)> outdp = [&](int cur,int par) {
    vector<int> vi;
    for(auto a:adj[cur])
      if(a != par && bet[a] == 0)
        vi.push_back(outdp(a, cur));
    return valv(vi);
  };

  vector<int> dp(n);  
  for(int i = 1; i < ((int) path.size()) - 1; i++)
    dp[path[i]] = outdp(path[i],path[i]);

  multiset<int> sst,sed;
  for(auto a:adj[st])
    if(bet[a] == 0) {
      sst.insert(outdp(a,a));
    }

  for(auto a:adj[ed])
    if(bet[a] == 0) {
      sed.insert(outdp(a,a));
    }

  int minans = n;
  multiset<int> vi,vi2;  

  auto val = [](multiset<int> &msi) {
    if(msi.empty())
      return 0;
    return int(msi.size()) + *msi.begin();
  };
  
  vector<int> pcomp1(path.size()),pcomp2(path.size());
  multiset<int> idk1,idk2;
  for(int i = 1; i < path.size() - 1;i++){
    if(i>1) {
      idk1.erase(idk1.find(dp[path[i-1]] + i - 2));
      idk1.insert(dp[path[i-1]] + i - 1);
    }
    if(i>0)
      idk1.insert(dp[path[i]] + i - 1);
    pcomp1[i] = *idk1.rbegin();
  }

  reverse(path.begin(),path.end());
  for(int i = 1; i < path.size() - 1;i++){
    if(i>1) {
      idk2.erase(idk2.find(dp[path[i-1]] + i - 2));
      idk2.insert(dp[path[i-1]] + i - 1);
    }
    if(i>0)
      idk2.insert(dp[path[i]] + i - 1);
    pcomp2[i] = *idk2.rbegin();
  }
  reverse(pcomp2.begin(),pcomp2.end());

  // for(auto a:pcomp1)
  //   cout<<a<<' ';
  // cout<<"\n";
  // for(auto a:pcomp2)
  //   cout<<a<<' ';
  // cout<<'\n';

  reverse(path.begin(),path.end());
  // for(auto a:path)
  //   cout<<dp[a]<<" ";
  // cout<<"\n";

  for(int i = 0; i < path.size() - 1;i++) {
    
    vector<int> vi1,vi2;
    for(auto a:sst)
      vi1.push_back(a);
    for(auto a:sed)
      vi2.push_back(a);
    if(i!=0)
      vi1.push_back(pcomp1[i]);
    if(i!=path.size() - 2)
      vi2.push_back(pcomp2[i + 1]);

//    for(auto a:vi1)
//      cout<<a<<" ";
//    cout<<"\n";
//    for(auto a:vi2)
//      cout<<a<<" ";
//    cout<<"\n\n";

    minans = min(minans,max(valv(vi1), valv(vi2)));

  }
  cout<<minans<<"\n";
}

Compilation message (stderr)

torrent.cpp: In lambda function:
torrent.cpp:42:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |     for(int i = 0; i < vi.size();i++)
      |                    ~~^~~~~~~~~~~
torrent.cpp: In function 'int main()':
torrent.cpp:81:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   81 |   for(int i = 1; i < path.size() - 1;i++){
      |                  ~~^~~~~~~~~~~~~~~~~
torrent.cpp:92:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   92 |   for(int i = 1; i < path.size() - 1;i++){
      |                  ~~^~~~~~~~~~~~~~~~~
torrent.cpp:115:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  115 |   for(int i = 0; i < path.size() - 1;i++) {
      |                  ~~^~~~~~~~~~~~~~~~~
torrent.cpp:124:9: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  124 |     if(i!=path.size() - 2)
      |        ~^~~~~~~~~~~~~~~~~
torrent.cpp:73:8: warning: variable 'val' set but not used [-Wunused-but-set-variable]
   73 |   auto val = [](multiset<int> &msi) {
      |        ^~~

• Subtask 1: 31 / 31
• Subtask 2: 0 / 69