#include<bits/stdc++.h>
using namespace std;
const int N=5e5+5;
int n;
int sz[N];
vector<int> adj[N];
int dfssz(int u,int p=0){
sz[u]=(adj[u].size()<2);
for(auto v:adj[u])if(v!=p)sz[u]+=dfssz(v,u);
return sz[u];
}
int centroid(int u,int cnt,int p=0){
for(auto v:adj[u])if(v!=p&&sz[v]>cnt/2)return centroid(v,cnt,u);
return u;
}
void dfs(int u,int p,vector<int> &comp){
if(adj[u].size()==1)comp.emplace_back(u);
for(auto v:adj[u])if(v!=p)dfs(v,u,comp);
}
int main(){
cin.tie(nullptr)->sync_with_stdio(false);
cin >> n;
for(int i=1;i<n;i++){
int u,v;
cin >> u >> v;
adj[u].emplace_back(v);
adj[v].emplace_back(u);
}
int c=centroid(1,dfssz(1));
vector<vector<int>> res;
for(auto v:adj[c]){
res.push_back({});
dfs(v,c,res.back());
}
priority_queue<pair<int,int>> pq;
for(int i=0;i<res.size();i++)pq.emplace(res[i].size(),i);
vector<pair<int,int>> ans;
while(!pq.empty()){
auto [s,i]=pq.top();
pq.pop();
if(pq.empty()){
ans.emplace_back(res[i].back(),c);
break;
}
auto [t,j]=pq.top();
pq.pop();
ans.emplace_back(res[i].back(),res[j].back());
res[i].pop_back();
res[j].pop_back();
if(--s)pq.emplace(s,i);
if(--t)pq.emplace(t,j);
}
cout << ans.size() << "\n";
for(auto [x,y]:ans)cout << x << " " << y << "\n";
}
Compilation message
net.cpp: In function 'int main()':
net.cpp:43:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
43 | for(int i=0;i<res.size();i++)pq.emplace(res[i].size(),i);
| ~^~~~~~~~~~~
net.cpp:46:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
46 | auto [s,i]=pq.top();
| ^
net.cpp:52:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
52 | auto [t,j]=pq.top();
| ^
net.cpp:61:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
61 | for(auto [x,y]:ans)cout << x << " " << y << "\n";
| ^
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 2 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 3 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 4 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 5 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 6 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 7 |
Correct |
3 ms |
13400 KB |
Output is correct |
| 8 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 9 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 10 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 11 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 12 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 13 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 14 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 15 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 16 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 17 |
Correct |
4 ms |
13144 KB |
Output is correct |
| 18 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 19 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 20 |
Correct |
3 ms |
12892 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 2 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 3 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 4 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 5 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 6 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 7 |
Correct |
3 ms |
13400 KB |
Output is correct |
| 8 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 9 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 10 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 11 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 12 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 13 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 14 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 15 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 16 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 17 |
Correct |
4 ms |
13144 KB |
Output is correct |
| 18 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 19 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 20 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 21 |
Correct |
4 ms |
13144 KB |
Output is correct |
| 22 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 23 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 24 |
Correct |
5 ms |
13148 KB |
Output is correct |
| 25 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 26 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 27 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 28 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 29 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 30 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 31 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 32 |
Correct |
3 ms |
12900 KB |
Output is correct |
| 33 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 34 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 35 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 36 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 37 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 38 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 39 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 40 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 41 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 42 |
Correct |
5 ms |
12892 KB |
Output is correct |
| 43 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 44 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 45 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 46 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 47 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 48 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 49 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 50 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 51 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 52 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 53 |
Correct |
5 ms |
12892 KB |
Output is correct |
| 54 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 55 |
Correct |
3 ms |
12988 KB |
Output is correct |
| 56 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 57 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 58 |
Correct |
5 ms |
12892 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 2 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 3 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 4 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 5 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 6 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 7 |
Correct |
3 ms |
13400 KB |
Output is correct |
| 8 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 9 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 10 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 11 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 12 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 13 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 14 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 15 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 16 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 17 |
Correct |
4 ms |
13144 KB |
Output is correct |
| 18 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 19 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 20 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 21 |
Correct |
4 ms |
13144 KB |
Output is correct |
| 22 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 23 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 24 |
Correct |
5 ms |
13148 KB |
Output is correct |
| 25 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 26 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 27 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 28 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 29 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 30 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 31 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 32 |
Correct |
3 ms |
12900 KB |
Output is correct |
| 33 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 34 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 35 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 36 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 37 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 38 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 39 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 40 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 41 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 42 |
Correct |
5 ms |
12892 KB |
Output is correct |
| 43 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 44 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 45 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 46 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 47 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 48 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 49 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 50 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 51 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 52 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 53 |
Correct |
5 ms |
12892 KB |
Output is correct |
| 54 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 55 |
Correct |
3 ms |
12988 KB |
Output is correct |
| 56 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 57 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 58 |
Correct |
5 ms |
12892 KB |
Output is correct |
| 59 |
Correct |
435 ms |
43360 KB |
Output is correct |
| 60 |
Correct |
401 ms |
36044 KB |
Output is correct |
| 61 |
Correct |
4 ms |
12888 KB |
Output is correct |
| 62 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 63 |
Correct |
332 ms |
37952 KB |
Output is correct |
| 64 |
Correct |
6 ms |
13404 KB |
Output is correct |
| 65 |
Correct |
12 ms |
14684 KB |
Output is correct |
| 66 |
Correct |
189 ms |
29012 KB |
Output is correct |
| 67 |
Correct |
606 ms |
46420 KB |
Output is correct |
| 68 |
Correct |
642 ms |
47628 KB |
Output is correct |
| 69 |
Correct |
14 ms |
14488 KB |
Output is correct |
| 70 |
Correct |
95 ms |
30324 KB |
Output is correct |
| 71 |
Correct |
339 ms |
70480 KB |
Output is correct |
| 72 |
Correct |
432 ms |
67776 KB |
Output is correct |
| 73 |
Correct |
54 ms |
18500 KB |
Output is correct |
| 74 |
Correct |
443 ms |
34196 KB |
Output is correct |
| 75 |
Correct |
36 ms |
17160 KB |
Output is correct |
| 76 |
Correct |
357 ms |
54752 KB |
Output is correct |
| 77 |
Correct |
379 ms |
55864 KB |
Output is correct |
| 78 |
Correct |
21 ms |
15704 KB |
Output is correct |
| 79 |
Correct |
556 ms |
44244 KB |
Output is correct |
| 80 |
Correct |
5 ms |
13148 KB |
Output is correct |
| 81 |
Correct |
83 ms |
25912 KB |
Output is correct |
| 82 |
Correct |
393 ms |
54156 KB |
Output is correct |
| 83 |
Correct |
381 ms |
33996 KB |
Output is correct |
| 84 |
Correct |
392 ms |
34460 KB |
Output is correct |
| 85 |
Correct |
412 ms |
34496 KB |
Output is correct |
| 86 |
Correct |
383 ms |
36432 KB |
Output is correct |
| 87 |
Correct |
386 ms |
36684 KB |
Output is correct |
