Submission #870613

#	Time	Username	Problem	Language	Result	Execution time	Memory
870613		epicci23	Papričice (COCI20_papricice)	C++17	15 / 110	3 ms	6560 KiB

papricice

#include "bits/stdc++.h"
using namespace std;
#define pb push_back
#define endl "\n" 
#define int long long
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()

/* stuff you should look for
 * int overflow, array bounds
 * special cases (n=1?)
 * do smth instead of nothing and stay organized
 * WRITE STUFF DOWN
 * DON'T GET STUCK ON ONE APPROACH
 * SIMPLIFY THE PROBLEM
 * READ THE STATEMENT CAREFULLY
  !!! if there is an specified/interesting smth(i.e. constraint) in the statement,
  then you must be careful about that   
*/
 
const int N = 2e5;

vector<int> v[N];
int dp[N];


void calc(int c,int p){
  dp[c]=1;
  for(int x:v[c]){
  	if(x==p) continue;
  	calc(x,c);
  	dp[c]+=dp[x];
  }
}

const int INF = 1e18;

int ans = INF;
multiset<int> ms;
int n;

void dfs(int c,int p){
  ms.erase(ms.find(dp[c]));
  if(c!=1){

    auto it = ms.lower_bound(dp[c]/2);

    if(it!=ms.end()){
      int u = (*it);
      ans=min(ans,max({u,dp[c]-u,n-dp[c]}) - min({u,dp[c]-u,n-dp[c]}));
    }
    if(it!=ms.begin()){
     it--;
     int u = (*it);
     ans=min(ans,max({u,dp[c]-u,n-dp[c]}) - min({u,dp[c]-u,n-dp[c]}));
    }

    it = ms.lower_bound((n-dp[c])/2);

    if(it!=ms.end()){
      int u = (*it);
      ans=min(ans,max({u,dp[c],n-dp[c]-u}) - min({u,dp[c],n-dp[c]-u}));
    }

    if(it!=ms.begin()){
      it--;
      int u = (*it);
      ans=min(ans,max({u,dp[c],n-dp[c]-u}) - min({u,dp[c],n-dp[c]-u}));
    }
  }
  for(int x:v[c]){
  	if(x==p) continue;
  	dfs(x,c);
  }
  ms.insert(dp[c]);
}


void solve(){
	
	cin >> n;
	for(int i=1;i<n;i++){
		int a,b;
		cin >> a >> b;
		v[a].pb(b);
		v[b].pb(a);
	}

	calc(1,0);

	for(int i=1;i<=n;i++) ms.insert(dp[i]);

	dfs(1,0);

    cout << ans << endl;
}

int32_t main(){

  cin.tie(0); ios::sync_with_stdio(0);
  
  int t=1;//cin >> t;
  while(t--) solve();

  return 0;
}

• Subtask 1: 15 / 15
• Subtask 2: 0 / 35
• Subtask 3: 0 / 60