#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define PB push_back
using pii = pair<int, int>;
using vi = vector<int>;
const int MXN = 5e5+5;
int n;
vi adj[MXN];
int leaf_cnt[MXN];
int root;
vector<vi> leaves;
void dfs1(int u, int p) {
leaf_cnt[u] = adj[u].size() == 1;
for(int v : adj[u]) {
if(v == p) continue;
dfs1(v, u);
leaf_cnt[u] += leaf_cnt[v];
}
}
int dfs2(int u, int p) {
for(int v : adj[u]) {
if(v == p) continue;
if(leaf_cnt[v] > (leaf_cnt[root]+1)/2) {
return dfs2(v, u);
}
}
return u;
}
void dfs3(int u, int p, vi &l) {
if(adj[u].size() == 1) l.PB(u);
for(int v : adj[u]) {
if(v == p) continue;
dfs3(v, u, l);
}
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for(int i = 0; i < n-1; i++) {
int a, b; cin >> a >> b;
adj[a].PB(b);
adj[b].PB(a);
}
for(int i = 1; i <= n; i++) {
if(adj[i].size() > 1) {
root = i;
dfs1(i, -1);
break;
}
}
root = dfs2(root, -1);
for(int u : adj[root]) {
vi l;
dfs3(u, root, l);
leaves.PB(l);
}
priority_queue<pii> PQ;
for(int i = 0; i < leaves.size(); i++) {
PQ.push({leaves[i].size(), i});
}
vector<pii> ans;
while(!PQ.empty()) {
if(PQ.size() == 1) {
auto p = PQ.top();
PQ.pop();
ans.PB({leaves[p.S].back(), root});
}
else {
auto p_a = PQ.top(); PQ.pop();
auto p_b = PQ.top(); PQ.pop();
ans.PB({leaves[p_a.S].back(), leaves[p_b.S].back()});
leaves[p_a.S].pop_back(), leaves[p_b.S].pop_back();
p_a.F--, p_b.F--;
if(p_a.F) PQ.push(p_a);
if(p_b.F) PQ.push(p_b);
}
}
cout << ans.size() << "\n";
for(auto p : ans) cout << p.F << " " << p.S << "\n";
return 0;
}
/*
6
1 2
2 3
2 4
5 4
6 4
8
1 2
2 3
3 4
4 5
3 6
3 7
3 8
*/
Compilation message
net.cpp: In function 'int main()':
net.cpp:73:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
73 | for(int i = 0; i < leaves.size(); i++) {
| ~~^~~~~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
5 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
12060 KB |
Output is correct |
3 |
Correct |
8 ms |
11988 KB |
Output is correct |
4 |
Correct |
6 ms |
11988 KB |
Output is correct |
5 |
Correct |
6 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
6 ms |
11964 KB |
Output is correct |
8 |
Correct |
6 ms |
11988 KB |
Output is correct |
9 |
Correct |
7 ms |
12092 KB |
Output is correct |
10 |
Correct |
7 ms |
11988 KB |
Output is correct |
11 |
Correct |
6 ms |
11988 KB |
Output is correct |
12 |
Correct |
9 ms |
11988 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
7 ms |
11988 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
6 ms |
12040 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
7 ms |
11988 KB |
Output is correct |
20 |
Correct |
6 ms |
11988 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
5 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
12060 KB |
Output is correct |
3 |
Correct |
8 ms |
11988 KB |
Output is correct |
4 |
Correct |
6 ms |
11988 KB |
Output is correct |
5 |
Correct |
6 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
6 ms |
11964 KB |
Output is correct |
8 |
Correct |
6 ms |
11988 KB |
Output is correct |
9 |
Correct |
7 ms |
12092 KB |
Output is correct |
10 |
Correct |
7 ms |
11988 KB |
Output is correct |
11 |
Correct |
6 ms |
11988 KB |
Output is correct |
12 |
Correct |
9 ms |
11988 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
7 ms |
11988 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
6 ms |
12040 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
7 ms |
11988 KB |
Output is correct |
20 |
Correct |
6 ms |
11988 KB |
Output is correct |
21 |
Correct |
6 ms |
11988 KB |
Output is correct |
22 |
Correct |
8 ms |
12244 KB |
Output is correct |
23 |
Correct |
9 ms |
12244 KB |
Output is correct |
24 |
Correct |
8 ms |
12244 KB |
Output is correct |
25 |
Correct |
7 ms |
12116 KB |
Output is correct |
26 |
Correct |
8 ms |
12116 KB |
Output is correct |
27 |
Correct |
7 ms |
12120 KB |
Output is correct |
28 |
Correct |
7 ms |
12116 KB |
Output is correct |
29 |
Correct |
6 ms |
12116 KB |
Output is correct |
30 |
Correct |
7 ms |
11988 KB |
Output is correct |
31 |
Correct |
7 ms |
12116 KB |
Output is correct |
32 |
Correct |
6 ms |
12008 KB |
Output is correct |
33 |
Correct |
6 ms |
12064 KB |
Output is correct |
34 |
Correct |
6 ms |
11988 KB |
Output is correct |
35 |
Correct |
6 ms |
11988 KB |
Output is correct |
36 |
Correct |
6 ms |
11988 KB |
Output is correct |
37 |
Correct |
7 ms |
12116 KB |
Output is correct |
38 |
Correct |
6 ms |
12116 KB |
Output is correct |
39 |
Correct |
6 ms |
11988 KB |
Output is correct |
40 |
Correct |
6 ms |
11988 KB |
Output is correct |
41 |
Correct |
6 ms |
11988 KB |
Output is correct |
42 |
Correct |
7 ms |
12116 KB |
Output is correct |
43 |
Correct |
7 ms |
12116 KB |
Output is correct |
44 |
Correct |
6 ms |
11964 KB |
Output is correct |
45 |
Correct |
8 ms |
11988 KB |
Output is correct |
46 |
Correct |
6 ms |
12116 KB |
Output is correct |
47 |
Correct |
7 ms |
12064 KB |
Output is correct |
48 |
Correct |
7 ms |
11988 KB |
Output is correct |
49 |
Correct |
7 ms |
12116 KB |
Output is correct |
50 |
Correct |
6 ms |
11988 KB |
Output is correct |
51 |
Correct |
6 ms |
11988 KB |
Output is correct |
52 |
Correct |
6 ms |
11988 KB |
Output is correct |
53 |
Correct |
6 ms |
12116 KB |
Output is correct |
54 |
Correct |
6 ms |
11988 KB |
Output is correct |
55 |
Correct |
6 ms |
11988 KB |
Output is correct |
56 |
Correct |
8 ms |
11988 KB |
Output is correct |
57 |
Correct |
6 ms |
12116 KB |
Output is correct |
58 |
Correct |
7 ms |
12152 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
5 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
12060 KB |
Output is correct |
3 |
Correct |
8 ms |
11988 KB |
Output is correct |
4 |
Correct |
6 ms |
11988 KB |
Output is correct |
5 |
Correct |
6 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
6 ms |
11964 KB |
Output is correct |
8 |
Correct |
6 ms |
11988 KB |
Output is correct |
9 |
Correct |
7 ms |
12092 KB |
Output is correct |
10 |
Correct |
7 ms |
11988 KB |
Output is correct |
11 |
Correct |
6 ms |
11988 KB |
Output is correct |
12 |
Correct |
9 ms |
11988 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
7 ms |
11988 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
6 ms |
12040 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
7 ms |
11988 KB |
Output is correct |
20 |
Correct |
6 ms |
11988 KB |
Output is correct |
21 |
Correct |
6 ms |
11988 KB |
Output is correct |
22 |
Correct |
8 ms |
12244 KB |
Output is correct |
23 |
Correct |
9 ms |
12244 KB |
Output is correct |
24 |
Correct |
8 ms |
12244 KB |
Output is correct |
25 |
Correct |
7 ms |
12116 KB |
Output is correct |
26 |
Correct |
8 ms |
12116 KB |
Output is correct |
27 |
Correct |
7 ms |
12120 KB |
Output is correct |
28 |
Correct |
7 ms |
12116 KB |
Output is correct |
29 |
Correct |
6 ms |
12116 KB |
Output is correct |
30 |
Correct |
7 ms |
11988 KB |
Output is correct |
31 |
Correct |
7 ms |
12116 KB |
Output is correct |
32 |
Correct |
6 ms |
12008 KB |
Output is correct |
33 |
Correct |
6 ms |
12064 KB |
Output is correct |
34 |
Correct |
6 ms |
11988 KB |
Output is correct |
35 |
Correct |
6 ms |
11988 KB |
Output is correct |
36 |
Correct |
6 ms |
11988 KB |
Output is correct |
37 |
Correct |
7 ms |
12116 KB |
Output is correct |
38 |
Correct |
6 ms |
12116 KB |
Output is correct |
39 |
Correct |
6 ms |
11988 KB |
Output is correct |
40 |
Correct |
6 ms |
11988 KB |
Output is correct |
41 |
Correct |
6 ms |
11988 KB |
Output is correct |
42 |
Correct |
7 ms |
12116 KB |
Output is correct |
43 |
Correct |
7 ms |
12116 KB |
Output is correct |
44 |
Correct |
6 ms |
11964 KB |
Output is correct |
45 |
Correct |
8 ms |
11988 KB |
Output is correct |
46 |
Correct |
6 ms |
12116 KB |
Output is correct |
47 |
Correct |
7 ms |
12064 KB |
Output is correct |
48 |
Correct |
7 ms |
11988 KB |
Output is correct |
49 |
Correct |
7 ms |
12116 KB |
Output is correct |
50 |
Correct |
6 ms |
11988 KB |
Output is correct |
51 |
Correct |
6 ms |
11988 KB |
Output is correct |
52 |
Correct |
6 ms |
11988 KB |
Output is correct |
53 |
Correct |
6 ms |
12116 KB |
Output is correct |
54 |
Correct |
6 ms |
11988 KB |
Output is correct |
55 |
Correct |
6 ms |
11988 KB |
Output is correct |
56 |
Correct |
8 ms |
11988 KB |
Output is correct |
57 |
Correct |
6 ms |
12116 KB |
Output is correct |
58 |
Correct |
7 ms |
12152 KB |
Output is correct |
59 |
Correct |
386 ms |
43060 KB |
Output is correct |
60 |
Correct |
390 ms |
35352 KB |
Output is correct |
61 |
Correct |
6 ms |
11988 KB |
Output is correct |
62 |
Correct |
6 ms |
11988 KB |
Output is correct |
63 |
Correct |
387 ms |
38032 KB |
Output is correct |
64 |
Correct |
8 ms |
12560 KB |
Output is correct |
65 |
Correct |
15 ms |
14264 KB |
Output is correct |
66 |
Correct |
148 ms |
31780 KB |
Output is correct |
67 |
Correct |
476 ms |
50540 KB |
Output is correct |
68 |
Correct |
510 ms |
51900 KB |
Output is correct |
69 |
Correct |
20 ms |
13724 KB |
Output is correct |
70 |
Correct |
98 ms |
29912 KB |
Output is correct |
71 |
Correct |
509 ms |
70508 KB |
Output is correct |
72 |
Correct |
384 ms |
66664 KB |
Output is correct |
73 |
Correct |
81 ms |
18192 KB |
Output is correct |
74 |
Correct |
403 ms |
34836 KB |
Output is correct |
75 |
Correct |
31 ms |
16636 KB |
Output is correct |
76 |
Correct |
366 ms |
54652 KB |
Output is correct |
77 |
Correct |
341 ms |
55580 KB |
Output is correct |
78 |
Correct |
28 ms |
15820 KB |
Output is correct |
79 |
Correct |
484 ms |
47724 KB |
Output is correct |
80 |
Correct |
8 ms |
12372 KB |
Output is correct |
81 |
Correct |
104 ms |
25720 KB |
Output is correct |
82 |
Correct |
409 ms |
53132 KB |
Output is correct |
83 |
Correct |
422 ms |
34072 KB |
Output is correct |
84 |
Correct |
402 ms |
34184 KB |
Output is correct |
85 |
Correct |
456 ms |
33968 KB |
Output is correct |
86 |
Correct |
422 ms |
35316 KB |
Output is correct |
87 |
Correct |
442 ms |
35476 KB |
Output is correct |