#include <bits/stdc++.h>
#ifdef DEBUG
#include "debug.h"
#else
#define debug(...) 0
#endif
typedef long long ll;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
int main() {
std::ios::sync_with_stdio(0);
std::cin.tie(0);
int n;
std::cin >> n;
std::vector<std::vector<int>> adj(n);
for (int i = 1; i < n; i++) {
int v, u;
std::cin >> v >> u;
v--; u--;
adj[v].push_back(u);
adj[u].push_back(v);
}
std::vector<int> leaf;
auto dfs = [&](auto self, int v, int p) -> void {
if (adj[v].size() == 1) {
leaf.push_back(v);
}
for (int u : adj[v]) {
if (u != p) {
self(self, u, v);
}
}
};
dfs(dfs, 0, 0);
int sz = leaf.size();
std::cout << (sz + 1) / 2 << '\n';
for (int i = 0; i + sz / 2 < sz; i++) {
std::cout << leaf[i] + 1 << ' ' << leaf[i + sz / 2] + 1 << '\n';
}
return 0;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
348 KB |
Output is correct |
2 |
Correct |
0 ms |
348 KB |
Output is correct |
3 |
Correct |
0 ms |
348 KB |
Output is correct |
4 |
Correct |
0 ms |
348 KB |
Output is correct |
5 |
Correct |
1 ms |
348 KB |
Output is correct |
6 |
Correct |
1 ms |
348 KB |
Output is correct |
7 |
Correct |
0 ms |
348 KB |
Output is correct |
8 |
Correct |
0 ms |
344 KB |
Output is correct |
9 |
Correct |
0 ms |
348 KB |
Output is correct |
10 |
Correct |
0 ms |
348 KB |
Output is correct |
11 |
Correct |
0 ms |
348 KB |
Output is correct |
12 |
Correct |
1 ms |
348 KB |
Output is correct |
13 |
Correct |
0 ms |
348 KB |
Output is correct |
14 |
Correct |
1 ms |
348 KB |
Output is correct |
15 |
Correct |
0 ms |
348 KB |
Output is correct |
16 |
Correct |
0 ms |
388 KB |
Output is correct |
17 |
Correct |
0 ms |
348 KB |
Output is correct |
18 |
Correct |
0 ms |
348 KB |
Output is correct |
19 |
Correct |
0 ms |
348 KB |
Output is correct |
20 |
Correct |
0 ms |
348 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
348 KB |
Output is correct |
2 |
Correct |
0 ms |
348 KB |
Output is correct |
3 |
Correct |
0 ms |
348 KB |
Output is correct |
4 |
Correct |
0 ms |
348 KB |
Output is correct |
5 |
Correct |
1 ms |
348 KB |
Output is correct |
6 |
Correct |
1 ms |
348 KB |
Output is correct |
7 |
Correct |
0 ms |
348 KB |
Output is correct |
8 |
Correct |
0 ms |
344 KB |
Output is correct |
9 |
Correct |
0 ms |
348 KB |
Output is correct |
10 |
Correct |
0 ms |
348 KB |
Output is correct |
11 |
Correct |
0 ms |
348 KB |
Output is correct |
12 |
Correct |
1 ms |
348 KB |
Output is correct |
13 |
Correct |
0 ms |
348 KB |
Output is correct |
14 |
Correct |
1 ms |
348 KB |
Output is correct |
15 |
Correct |
0 ms |
348 KB |
Output is correct |
16 |
Correct |
0 ms |
388 KB |
Output is correct |
17 |
Correct |
0 ms |
348 KB |
Output is correct |
18 |
Correct |
0 ms |
348 KB |
Output is correct |
19 |
Correct |
0 ms |
348 KB |
Output is correct |
20 |
Correct |
0 ms |
348 KB |
Output is correct |
21 |
Correct |
0 ms |
348 KB |
Output is correct |
22 |
Correct |
1 ms |
604 KB |
Output is correct |
23 |
Correct |
1 ms |
348 KB |
Output is correct |
24 |
Correct |
1 ms |
604 KB |
Output is correct |
25 |
Correct |
1 ms |
344 KB |
Output is correct |
26 |
Correct |
1 ms |
348 KB |
Output is correct |
27 |
Correct |
1 ms |
348 KB |
Output is correct |
28 |
Correct |
1 ms |
348 KB |
Output is correct |
29 |
Correct |
1 ms |
344 KB |
Output is correct |
30 |
Correct |
0 ms |
348 KB |
Output is correct |
31 |
Correct |
1 ms |
348 KB |
Output is correct |
32 |
Correct |
1 ms |
348 KB |
Output is correct |
33 |
Correct |
0 ms |
348 KB |
Output is correct |
34 |
Correct |
0 ms |
348 KB |
Output is correct |
35 |
Correct |
0 ms |
344 KB |
Output is correct |
36 |
Correct |
1 ms |
348 KB |
Output is correct |
37 |
Correct |
0 ms |
348 KB |
Output is correct |
38 |
Correct |
1 ms |
344 KB |
Output is correct |
39 |
Correct |
1 ms |
760 KB |
Output is correct |
40 |
Correct |
1 ms |
344 KB |
Output is correct |
41 |
Correct |
0 ms |
344 KB |
Output is correct |
42 |
Correct |
1 ms |
348 KB |
Output is correct |
43 |
Correct |
0 ms |
348 KB |
Output is correct |
44 |
Correct |
0 ms |
344 KB |
Output is correct |
45 |
Correct |
0 ms |
348 KB |
Output is correct |
46 |
Correct |
1 ms |
348 KB |
Output is correct |
47 |
Correct |
0 ms |
348 KB |
Output is correct |
48 |
Correct |
0 ms |
348 KB |
Output is correct |
49 |
Correct |
1 ms |
348 KB |
Output is correct |
50 |
Correct |
0 ms |
348 KB |
Output is correct |
51 |
Correct |
0 ms |
348 KB |
Output is correct |
52 |
Correct |
1 ms |
344 KB |
Output is correct |
53 |
Correct |
1 ms |
348 KB |
Output is correct |
54 |
Correct |
0 ms |
348 KB |
Output is correct |
55 |
Correct |
1 ms |
344 KB |
Output is correct |
56 |
Correct |
0 ms |
348 KB |
Output is correct |
57 |
Correct |
1 ms |
348 KB |
Output is correct |
58 |
Correct |
1 ms |
604 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
348 KB |
Output is correct |
2 |
Correct |
0 ms |
348 KB |
Output is correct |
3 |
Correct |
0 ms |
348 KB |
Output is correct |
4 |
Correct |
0 ms |
348 KB |
Output is correct |
5 |
Correct |
1 ms |
348 KB |
Output is correct |
6 |
Correct |
1 ms |
348 KB |
Output is correct |
7 |
Correct |
0 ms |
348 KB |
Output is correct |
8 |
Correct |
0 ms |
344 KB |
Output is correct |
9 |
Correct |
0 ms |
348 KB |
Output is correct |
10 |
Correct |
0 ms |
348 KB |
Output is correct |
11 |
Correct |
0 ms |
348 KB |
Output is correct |
12 |
Correct |
1 ms |
348 KB |
Output is correct |
13 |
Correct |
0 ms |
348 KB |
Output is correct |
14 |
Correct |
1 ms |
348 KB |
Output is correct |
15 |
Correct |
0 ms |
348 KB |
Output is correct |
16 |
Correct |
0 ms |
388 KB |
Output is correct |
17 |
Correct |
0 ms |
348 KB |
Output is correct |
18 |
Correct |
0 ms |
348 KB |
Output is correct |
19 |
Correct |
0 ms |
348 KB |
Output is correct |
20 |
Correct |
0 ms |
348 KB |
Output is correct |
21 |
Correct |
0 ms |
348 KB |
Output is correct |
22 |
Correct |
1 ms |
604 KB |
Output is correct |
23 |
Correct |
1 ms |
348 KB |
Output is correct |
24 |
Correct |
1 ms |
604 KB |
Output is correct |
25 |
Correct |
1 ms |
344 KB |
Output is correct |
26 |
Correct |
1 ms |
348 KB |
Output is correct |
27 |
Correct |
1 ms |
348 KB |
Output is correct |
28 |
Correct |
1 ms |
348 KB |
Output is correct |
29 |
Correct |
1 ms |
344 KB |
Output is correct |
30 |
Correct |
0 ms |
348 KB |
Output is correct |
31 |
Correct |
1 ms |
348 KB |
Output is correct |
32 |
Correct |
1 ms |
348 KB |
Output is correct |
33 |
Correct |
0 ms |
348 KB |
Output is correct |
34 |
Correct |
0 ms |
348 KB |
Output is correct |
35 |
Correct |
0 ms |
344 KB |
Output is correct |
36 |
Correct |
1 ms |
348 KB |
Output is correct |
37 |
Correct |
0 ms |
348 KB |
Output is correct |
38 |
Correct |
1 ms |
344 KB |
Output is correct |
39 |
Correct |
1 ms |
760 KB |
Output is correct |
40 |
Correct |
1 ms |
344 KB |
Output is correct |
41 |
Correct |
0 ms |
344 KB |
Output is correct |
42 |
Correct |
1 ms |
348 KB |
Output is correct |
43 |
Correct |
0 ms |
348 KB |
Output is correct |
44 |
Correct |
0 ms |
344 KB |
Output is correct |
45 |
Correct |
0 ms |
348 KB |
Output is correct |
46 |
Correct |
1 ms |
348 KB |
Output is correct |
47 |
Correct |
0 ms |
348 KB |
Output is correct |
48 |
Correct |
0 ms |
348 KB |
Output is correct |
49 |
Correct |
1 ms |
348 KB |
Output is correct |
50 |
Correct |
0 ms |
348 KB |
Output is correct |
51 |
Correct |
0 ms |
348 KB |
Output is correct |
52 |
Correct |
1 ms |
344 KB |
Output is correct |
53 |
Correct |
1 ms |
348 KB |
Output is correct |
54 |
Correct |
0 ms |
348 KB |
Output is correct |
55 |
Correct |
1 ms |
344 KB |
Output is correct |
56 |
Correct |
0 ms |
348 KB |
Output is correct |
57 |
Correct |
1 ms |
348 KB |
Output is correct |
58 |
Correct |
1 ms |
604 KB |
Output is correct |
59 |
Correct |
226 ms |
29004 KB |
Output is correct |
60 |
Correct |
253 ms |
32204 KB |
Output is correct |
61 |
Correct |
1 ms |
344 KB |
Output is correct |
62 |
Correct |
0 ms |
600 KB |
Output is correct |
63 |
Correct |
177 ms |
26060 KB |
Output is correct |
64 |
Correct |
2 ms |
856 KB |
Output is correct |
65 |
Correct |
7 ms |
2396 KB |
Output is correct |
66 |
Correct |
60 ms |
16308 KB |
Output is correct |
67 |
Correct |
334 ms |
37448 KB |
Output is correct |
68 |
Correct |
323 ms |
38504 KB |
Output is correct |
69 |
Correct |
4 ms |
1368 KB |
Output is correct |
70 |
Correct |
49 ms |
11280 KB |
Output is correct |
71 |
Correct |
165 ms |
35236 KB |
Output is correct |
72 |
Correct |
183 ms |
34512 KB |
Output is correct |
73 |
Correct |
47 ms |
8944 KB |
Output is correct |
74 |
Correct |
249 ms |
31152 KB |
Output is correct |
75 |
Correct |
18 ms |
4316 KB |
Output is correct |
76 |
Correct |
204 ms |
34924 KB |
Output is correct |
77 |
Correct |
186 ms |
35252 KB |
Output is correct |
78 |
Correct |
15 ms |
4184 KB |
Output is correct |
79 |
Correct |
332 ms |
36548 KB |
Output is correct |
80 |
Correct |
1 ms |
604 KB |
Output is correct |
81 |
Correct |
49 ms |
11576 KB |
Output is correct |
82 |
Correct |
217 ms |
33172 KB |
Output is correct |
83 |
Correct |
340 ms |
31376 KB |
Output is correct |
84 |
Correct |
262 ms |
31012 KB |
Output is correct |
85 |
Correct |
267 ms |
31036 KB |
Output is correct |
86 |
Correct |
265 ms |
32200 KB |
Output is correct |
87 |
Correct |
262 ms |
32256 KB |
Output is correct |