Submission #376320

#	Time	Username	Problem	Language	Result	Execution time	Memory
376320		errorgorn	Papričice (COCI20_papricice)	C++17	110 / 110	301 ms	37348 KiB

papricice

//雪花飄飄北風嘯嘯
//天地一片蒼茫

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
#define ll long long
#define ii pair<ll,ll>
#define iii pair<ii,ll>
#define fi first
#define se second
#define endl '\n'
#define debug(x) cout << #x << " is " << x << endl

#define pub push_back
#define pob pop_back
#define puf push_front
#define pof pop_front
#define lb lower_bound
#define up upper_bound

#define rep(x,start,end) for(auto x=(start)-((start)>(end));x!=(end)-((start)>(end));((start)<(end)?x++:x--))
#define all(x) (x).begin(),(x).end()
#define sz(x) (int)(x).size()

#define indexed_set tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>
//change less to less_equal for non distinct pbds, but erase will bug

mt19937 rng(chrono::system_clock::now().time_since_epoch().count());

int n;
vector<int> al[200005];
set<int> s[200005];
int sz[200005];

void dfs_sz(int i,int p){
	sz[i]=1;
	
	for (auto &it:al[i]){
		if (it==p) continue;
		dfs_sz(it,i);
		sz[i]+=sz[it];
	}
}

ll ans=1e9;

ll calc(int i,int j){
	int k=n-i-j;
	int arr[3]={i,j,k};
	sort(arr,arr+3);
	return arr[2]-arr[0];
}

void dfs(int i,int p){
	for (auto &it:al[i]){
		if (it==p) continue;
		
		dfs(it,i);
		
		if (sz(s[it])>sz(s[i])) swap(s[it],s[i]);
		
		for (auto &it:s[it]){
			auto temp=s[i].lb((n-it)/2);
			if (temp!=s[i].begin()){
				ans=min(ans,calc(it,*prev(temp)));
			}
			if (temp!=s[i].end()){
				ans=min(ans,calc(it,*temp));
			}
		}
		
		s[i].insert(all(s[it]));
		
		// auto temp=s[i];
		// for (auto &it:s[it]){
			// s[i].insert(it);
			// for (auto &it2:temp) ans=min(ans,calc(it,it2));
		// }
	}
	
	auto temp=s[i].lb(sz[i]/2);
	if (temp!=s[i].begin()){
		ans=min(ans,calc(sz[i]-*prev(temp),*prev(temp)));
	}
	if (temp!=s[i].end()){
		ans=min(ans,calc(sz[i]-*temp,*temp));
	}
	
	//for (auto &it:s[i]) ans=min(ans,calc(sz[i]-it,it));
	
	s[i].insert(sz[i]);
}

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin.exceptions(ios::badbit | ios::failbit);
	
	cin>>n;
	
	int a,b;
	rep(x,1,n){
		cin>>a>>b;
		al[a].pub(b);
		al[b].pub(a);
	}
	
	dfs_sz(1,-1);
	dfs(1,-1);
	
	cout<<ans<<endl;
}

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