Submission #1191593

#	Time	Username	Problem	Language	Result	Execution time	Memory
1191593		SmuggingSpun	Papričice (COCI20_papricice)	C++20	15 / 110	41 ms	14404 KiB

papricice

#include<bits/stdc++.h>
#define taskname "D"
using namespace std;
template<class T>void minimize(T& a, T b){
	if(a > b){
		a = b;
	}
}
template<class T>void maximize(T& a, T b){
	if(a < b){
		a = b;
	}
}
const int lim = 2e5 + 5;
vector<int>g[lim];
int n, u[lim], v[lim];
namespace sub1{
	const int lim = 205;
	int cnt;
	bitset<lim>vis;
	void dfs(int s, const int& i1, const int& i2){
		cnt++;
		vis.set(s);
		for(int& i : g[s]){
			if(i != i1 && i != i2){
				int d = u[i] ^ v[i] ^ s;
				if(!vis.test(d)){
					dfs(d, i1, i2);
				}
			}
		}
	}
	void solve(){
		int ans = n;
		for(int i = 1; i < n; i++){
			for(int j = i + 1; j < n; j++){
				vis.reset();
				int max_cnt = 0, min_cnt = n;
				for(int k = 1; k <= n; k++){
					if(!vis.test(k)){
						cnt = 0;
						dfs(k, i, j);
						minimize(min_cnt, cnt);
						maximize(max_cnt, cnt);
					}
				}
				minimize(ans, max_cnt - min_cnt);
			}
		}
		cout << ans;
	}
}
namespace sub23{
	set<int>S[lim];
	int ans = INT_MAX, cnt[lim];
	void dfs_1(int s, int p = -1){
		cnt[s] = 1;
		for(int& i : g[s]){
			int d = u[i] ^ v[i] ^ s;
			if(d != p){
				dfs_1(d, s);
				cnt[s] += cnt[d];
			}
		}
	}
	void update(int other, set<int>& S){
		int remain = n - other;
		auto it = S.upper_bound(remain >> 1);
		if(it != S.end()){
			minimize(ans, max(other, *it) - min(other, remain - *it));
		}
		if(it != S.begin()){
			it = prev(it);
			minimize(ans, max(other, remain - *it) - min(other, *it));
		}
	}
	void dfs_2(int s, int p = -1){
		for(int& i : g[s]){
			int d = u[i] ^ v[i] ^ s;
			if(d != p){
				dfs_2(d, s);
				if(S[s].size() < S[d].size()){
					swap(S[s], S[d]);
				}
				for(const int& x : S[d]){
					update(x, S[s]);
				}
				for(const int& x : S[d]){
					S[s].insert(s);
				}
			}
		}
		update(n - cnt[s], S[s]);
	}
	void solve(){
		dfs_1(1);
		dfs_2(1);
		cout << ans;
	}
}
int main(){
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	if(fopen(taskname".inp", "r")){
		freopen(taskname".inp", "r", stdin);
	}
	cin >> n;
	for(int i = 1; i < n; i++){
		cin >> u[i] >> v[i];
		g[u[i]].emplace_back(i);
		g[v[i]].emplace_back(i);
	}
	if(n <= 200){
		sub1::solve();
	}
	else{
		sub23::solve();
	}
}

Compilation message (stderr)

papricice.cpp: In function 'int main()':
papricice.cpp:104:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  104 |                 freopen(taskname".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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