This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
const int MOD = 1e9+7;
int N;
vector<int> adjList[200001];
int upper[200001];
int lower[200001];
int ans = (1<<30);
void DFS(int node, int parent) {
int total = 1;
for (auto child: adjList[node]) {
if (child == parent) continue;
DFS(child, node);
total += upper[child]+lower[child];
}
upper[node] = total;
for (auto child: adjList[node]) {
if (child == parent) continue;
if (total-(upper[child]+lower[child]) < abs(upper[node]-lower[node])
|| (total-(upper[child]+lower[child]) == abs(upper[node]-lower[node])
&& total-(upper[child]+lower[child]) <= upper[child]+lower[child])) {
upper[node] = total-(upper[child]+lower[child]);
lower[node] = upper[child]+lower[child];
}
if (total-lower[child] < abs(upper[node]-lower[node])
|| (total-lower[child] == abs(upper[node]-lower[node])
&& total-lower[child] <= lower[child])) {
upper[node] = total-lower[child];
lower[node] = lower[child];
}
}
if (adjList[node].size() > 1) {
int mx = max(N-total, max(upper[node], lower[node]));
int mn = min(N-total, min(upper[node], lower[node]));
ans = min(ans, mx-mn);
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> N;
for (int i = 1; i < N; i++) {
int u, v;
cin >> u >> v;
adjList[u].push_back(v);
adjList[v].push_back(u);
}
for (int i = 1; i <= N; i++) {
// Start from a leaf node
if (adjList[i].size() == 1) {
DFS(i, -1);
break;
}
}
cout << ans << "\n";
}
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