#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define endl '\n'
const int N = 2e5 + 5;
int n;
vector<int> adj[N];
int subtree[N];
vector<int> path;
void calc(int node,int par){
subtree[node] = 1;
for(auto ch : adj[node]){
if(ch == par) continue;
calc(ch,node);
subtree[node] += subtree[ch];
}
}
int ans = 1e9;
void dfs1(int node,int par){
if(node != 1) path.push_back(subtree[node]);
int a = n , c = subtree[node];
if(path.size() >= 2){
int idx = (int)path.size() - 1 - (upper_bound(path.rbegin(),path.rend(),2*c) - path.rbegin() - 1);
if(idx >= 0 && idx < path.size()-1 && path[idx] >= (a + c + 1) / 2) ans = min(ans , c - (a - path[idx]));
idx = (int)path.size() - 1 - (lower_bound(path.rbegin(),path.rend(),2*c) - path.rbegin());
if(idx < path.size()-1 && path[idx] <= (a + c) / 2) ans = min(ans , a - path[idx] - c);
idx = (int)path.size() - 1 -(lower_bound(path.rbegin(),path.rend(),max(a-c,2*c)) - path.rbegin());
if(idx < path.size()-1) ans = min(ans , path[idx] - c - (a - path[idx]));
idx = (int)path.size() - 1 - (upper_bound(path.rbegin(),path.rend(),min(a-c,2*c)) - path.rbegin() - 1);
if(idx < path.size()-1) ans = min(ans , a - 2*path[idx] + c);
idx = (int)path.size() - 1 - (upper_bound(path.rbegin(),path.rend(),(a + c) / 2) - path.rbegin() - 1);
if(idx >= 0 && idx < path.size()-1 && path[idx] >= a - c) ans = min(ans , 2 * c - path[idx]);
idx = (int)path.size() - 1 - (lower_bound(path.rbegin(),path.rend(),(a + c + 1) / 2) - path.rbegin());
if(idx < path.size()-1 && path[idx] <= a - c) ans = min(ans , path[idx] - 2*c);
}
for(auto ch : adj[node]){
if(ch == par) continue;
dfs1(ch,node);
}
if(node != 1) path.pop_back();
}
multiset<int> st;
void dfs2(int node,int par){
int a = n;
int c = subtree[node];
if(st.size()){
auto it = st.upper_bound((a - c) / 2);
if(it != st.begin() && (*(--it)) >= c) ans = min(ans , a - (*it) - 2*c);
it = st.lower_bound((a + c + 1) / 2);
if(it != st.end() && (*it) <= c) ans = min(ans , 2*c + (*it) - a);
it = st.upper_bound(min(c,a-2*c));
if(it != st.begin()) ans = min(ans , a - 2*(*(--it)) - c);
it = st.lower_bound(max(c,a-2*c));
if(it != st.end()) ans = min(ans , 2*(*it) + c - a);
it = st.upper_bound((a - c) / 2);
if(it != st.begin() && (*(--it)) >= a - 2*c) ans = min(ans , c - (*it));
it = st.lower_bound((a - c + 1) / 2);
if(it != st.end() && (*it) <= a - 2*c) ans = min(ans , (*it) - c);
}
for(auto ch : adj[node]){
if(ch == par) continue;
dfs2(ch,node);
}
st.insert(subtree[node]);
}
void solve(){
cin>>n;
for(int i=0;i<n-1;i++){
int a,b;
cin>>a>>b;
adj[a].push_back(b);
adj[b].push_back(a);
}
calc(1,0);
dfs1(1,0);
dfs2(1,0);
cout<<ans<<endl;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int t=1;
//cin>>t;
while(t--){
solve();
}
return 0;
}
Compilation message
papricice.cpp: In function 'void dfs1(int, int)':
papricice.cpp:24:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
24 | if(idx >= 0 && idx < path.size()-1 && path[idx] >= (a + c + 1) / 2) ans = min(ans , c - (a - path[idx]));
| ~~~~^~~~~~~~~~~~~~~
papricice.cpp:26:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
26 | if(idx < path.size()-1 && path[idx] <= (a + c) / 2) ans = min(ans , a - path[idx] - c);
| ~~~~^~~~~~~~~~~~~~~
papricice.cpp:28:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
28 | if(idx < path.size()-1) ans = min(ans , path[idx] - c - (a - path[idx]));
| ~~~~^~~~~~~~~~~~~~~
papricice.cpp:30:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
30 | if(idx < path.size()-1) ans = min(ans , a - 2*path[idx] + c);
| ~~~~^~~~~~~~~~~~~~~
papricice.cpp:32:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
32 | if(idx >= 0 && idx < path.size()-1 && path[idx] >= a - c) ans = min(ans , 2 * c - path[idx]);
| ~~~~^~~~~~~~~~~~~~~
papricice.cpp:34:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
34 | if(idx < path.size()-1 && path[idx] <= a - c) ans = min(ans , path[idx] - 2*c);
| ~~~~^~~~~~~~~~~~~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
2 ms |
5720 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
5724 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
2 ms |
5720 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
5724 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
2 ms |
5720 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
5724 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
