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- #include <bits/stdc++.h>
- using namespace std;
- vector<vector<pair<int, bool> > > G;
- vector<bool> odwiedz;
- vector<int> zlekrawedzie;
- vector<int> wynik;
- int answ = 1e9;
- void DFS (int v)
- {
- odwiedz[v] = true;
- for (int i = 0; i < int(G[v].size()); ++i)
- {
- int u = G[v][i].first;
- if (!odwiedz[u])
- {
- DFS(u);
- zlekrawedzie[v] += zlekrawedzie[u] + int(G[v][i].second);
- }
- }
- }
- void DFS2 (int v)
- {
- odwiedz[v] = true;
- for (int i = 0; i < int(G[v].size()); ++i)
- {
- int u = G[v][i].first;
- if(!odwiedz[u])
- {
- if(G[v][i].second)
- wynik[u] = wynik[v] + 1;
- else
- wynik[u] = wynik[v] - 1;
- DFS2(u);
- }
- }
- }
- int main ()
- {
- ios_base::sync_with_stdio(0);
- cin.tie(0);
- int N;
- cin >> N;
- G.resize(N);
- odwiedz.resize(N);
- zlekrawedzie.resize(N);
- for(int i = 0; i < N - 1; ++i)
- {
- int a, b;
- cin >> a >> b;
- --a;
- --b;
- G[a].emplace_back(b, true);
- G[b].emplace_back(a, false);
- }
- DFS(0);
- wynik.resize(N);
- wynik[0] = zlekrawedzie[0];
- DFS2(0);
- for (int i = 0; i < N; ++i)
- answ = min(answ, zlekrawedzie[i]);
- cout << answ;
- }
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