#include<bits/stdc++.h>
using namespace std;
const int N = 5e5 + 10;
int n, 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() << endl;
for(auto [x,y] : ans) cout << x << " " << y << endl;
}
Compilation message
net.cpp: In function 'int main()':
net.cpp:44:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
44 | for (int i = 0; i < res.size(); i++) pq.emplace(res[i].size(),i);
| ~~^~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
12944 KB |
Output is correct |
| 2 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 3 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 4 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 5 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 6 |
Correct |
3 ms |
12944 KB |
Output is correct |
| 7 |
Correct |
4 ms |
13148 KB |
Output is correct |
| 8 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 9 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 10 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 11 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 12 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 13 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 14 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 15 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 16 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 17 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 18 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 19 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 20 |
Correct |
2 ms |
12892 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
12944 KB |
Output is correct |
| 2 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 3 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 4 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 5 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 6 |
Correct |
3 ms |
12944 KB |
Output is correct |
| 7 |
Correct |
4 ms |
13148 KB |
Output is correct |
| 8 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 9 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 10 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 11 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 12 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 13 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 14 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 15 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 16 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 17 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 18 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 19 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 20 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 21 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 22 |
Correct |
4 ms |
13128 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 |
12888 KB |
Output is correct |
| 27 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 28 |
Correct |
4 ms |
13144 KB |
Output is correct |
| 29 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 30 |
Correct |
3 ms |
13088 KB |
Output is correct |
| 31 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 32 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 33 |
Correct |
3 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 |
12892 KB |
Output is correct |
| 41 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 42 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 43 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 44 |
Correct |
3 ms |
12888 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 |
12956 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 |
3 ms |
12892 KB |
Output is correct |
| 54 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 55 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 56 |
Correct |
3 ms |
12928 KB |
Output is correct |
| 57 |
Correct |
3 ms |
12940 KB |
Output is correct |
| 58 |
Correct |
4 ms |
12892 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
12944 KB |
Output is correct |
| 2 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 3 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 4 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 5 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 6 |
Correct |
3 ms |
12944 KB |
Output is correct |
| 7 |
Correct |
4 ms |
13148 KB |
Output is correct |
| 8 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 9 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 10 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 11 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 12 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 13 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 14 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 15 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 16 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 17 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 18 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 19 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 20 |
Correct |
2 ms |
12892 KB |
Output is correct |
| 21 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 22 |
Correct |
4 ms |
13128 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 |
12888 KB |
Output is correct |
| 27 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 28 |
Correct |
4 ms |
13144 KB |
Output is correct |
| 29 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 30 |
Correct |
3 ms |
13088 KB |
Output is correct |
| 31 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 32 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 33 |
Correct |
3 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 |
12892 KB |
Output is correct |
| 41 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 42 |
Correct |
3 ms |
12888 KB |
Output is correct |
| 43 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 44 |
Correct |
3 ms |
12888 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 |
12956 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 |
3 ms |
12892 KB |
Output is correct |
| 54 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 55 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 56 |
Correct |
3 ms |
12928 KB |
Output is correct |
| 57 |
Correct |
3 ms |
12940 KB |
Output is correct |
| 58 |
Correct |
4 ms |
12892 KB |
Output is correct |
| 59 |
Correct |
449 ms |
50840 KB |
Output is correct |
| 60 |
Correct |
497 ms |
42760 KB |
Output is correct |
| 61 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 62 |
Correct |
3 ms |
12892 KB |
Output is correct |
| 63 |
Correct |
408 ms |
43300 KB |
Output is correct |
| 64 |
Correct |
4 ms |
13404 KB |
Output is correct |
| 65 |
Correct |
11 ms |
14940 KB |
Output is correct |
| 66 |
Correct |
91 ms |
31316 KB |
Output is correct |
| 67 |
Correct |
471 ms |
52992 KB |
Output is correct |
| 68 |
Correct |
463 ms |
54276 KB |
Output is correct |
| 69 |
Correct |
17 ms |
14744 KB |
Output is correct |
| 70 |
Correct |
146 ms |
32804 KB |
Output is correct |
| 71 |
Correct |
548 ms |
77264 KB |
Output is correct |
| 72 |
Correct |
540 ms |
74668 KB |
Output is correct |
| 73 |
Correct |
85 ms |
20188 KB |
Output is correct |
| 74 |
Correct |
462 ms |
40760 KB |
Output is correct |
| 75 |
Correct |
50 ms |
17928 KB |
Output is correct |
| 76 |
Correct |
520 ms |
61488 KB |
Output is correct |
| 77 |
Correct |
536 ms |
62252 KB |
Output is correct |
| 78 |
Correct |
36 ms |
16528 KB |
Output is correct |
| 79 |
Correct |
439 ms |
50772 KB |
Output is correct |
| 80 |
Correct |
6 ms |
13144 KB |
Output is correct |
| 81 |
Correct |
140 ms |
27888 KB |
Output is correct |
| 82 |
Correct |
515 ms |
59644 KB |
Output is correct |
| 83 |
Correct |
454 ms |
40952 KB |
Output is correct |
| 84 |
Correct |
488 ms |
41136 KB |
Output is correct |
| 85 |
Correct |
467 ms |
41536 KB |
Output is correct |
| 86 |
Correct |
488 ms |
43048 KB |
Output is correct |
| 87 |
Correct |
492 ms |
43032 KB |
Output is correct |
