#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define F first
#define S second
using namespace std;
int n, pre[300005], sz[300005], cnt;
vector<int> E[300005], leaf;
vector<pii> ans;
void dfs(int u)
{
sz[u] = (E[u].size() == 1);
for (auto v : E[u])
if(pre[u] != v)
{
pre[v] = u;
dfs(v);
sz[u] += sz[v];
}
}
void collect(int u)
{
if(E[u].size() == 1)
leaf.emplace_back(u);
for (auto v : E[u])
if(pre[u] != v)
{
pre[v] = u;
collect(v);
}
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
cin >> n;
for (int i = 1; i < n; i++)
{
int u, v;
cin >> u >> v;
E[u].emplace_back(v);
E[v].emplace_back(u);
}
dfs(1);
int c = 1;
for (int i = 1; i <= n; i++)
{
bool flag = (sz[1] - sz[i] <= sz[1] / 2);
for(auto j : E[i])
if(pre[i] != j && sz[j] > sz[1] / 2)
flag = 0;
if(flag)
c = i;
}
pre[c] = 0;
collect(c);
for (int i = 0; i < sz[1] / 2; i++)
ans.emplace_back(pii(leaf[i], leaf[i + (sz[1] + 1) / 2]));
if(sz[1] & 1)
ans.emplace_back(pii(c, leaf[sz[1] / 2]));
cout << ans.size() << '\n';
for(auto [i, j] : ans)
cout << i << ' ' << j << '\n';
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
4 ms |
7380 KB |
Output is correct |
2 |
Correct |
4 ms |
7380 KB |
Output is correct |
3 |
Correct |
4 ms |
7380 KB |
Output is correct |
4 |
Correct |
4 ms |
7320 KB |
Output is correct |
5 |
Correct |
4 ms |
7380 KB |
Output is correct |
6 |
Correct |
4 ms |
7380 KB |
Output is correct |
7 |
Correct |
4 ms |
7380 KB |
Output is correct |
8 |
Correct |
4 ms |
7252 KB |
Output is correct |
9 |
Correct |
4 ms |
7252 KB |
Output is correct |
10 |
Correct |
4 ms |
7380 KB |
Output is correct |
11 |
Correct |
4 ms |
7380 KB |
Output is correct |
12 |
Correct |
4 ms |
7380 KB |
Output is correct |
13 |
Correct |
4 ms |
7380 KB |
Output is correct |
14 |
Correct |
4 ms |
7380 KB |
Output is correct |
15 |
Correct |
4 ms |
7380 KB |
Output is correct |
16 |
Correct |
4 ms |
7376 KB |
Output is correct |
17 |
Correct |
4 ms |
7380 KB |
Output is correct |
18 |
Correct |
4 ms |
7388 KB |
Output is correct |
19 |
Correct |
3 ms |
7276 KB |
Output is correct |
20 |
Correct |
4 ms |
7384 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
4 ms |
7380 KB |
Output is correct |
2 |
Correct |
4 ms |
7380 KB |
Output is correct |
3 |
Correct |
4 ms |
7380 KB |
Output is correct |
4 |
Correct |
4 ms |
7320 KB |
Output is correct |
5 |
Correct |
4 ms |
7380 KB |
Output is correct |
6 |
Correct |
4 ms |
7380 KB |
Output is correct |
7 |
Correct |
4 ms |
7380 KB |
Output is correct |
8 |
Correct |
4 ms |
7252 KB |
Output is correct |
9 |
Correct |
4 ms |
7252 KB |
Output is correct |
10 |
Correct |
4 ms |
7380 KB |
Output is correct |
11 |
Correct |
4 ms |
7380 KB |
Output is correct |
12 |
Correct |
4 ms |
7380 KB |
Output is correct |
13 |
Correct |
4 ms |
7380 KB |
Output is correct |
14 |
Correct |
4 ms |
7380 KB |
Output is correct |
15 |
Correct |
4 ms |
7380 KB |
Output is correct |
16 |
Correct |
4 ms |
7376 KB |
Output is correct |
17 |
Correct |
4 ms |
7380 KB |
Output is correct |
18 |
Correct |
4 ms |
7388 KB |
Output is correct |
19 |
Correct |
3 ms |
7276 KB |
Output is correct |
20 |
Correct |
4 ms |
7384 KB |
Output is correct |
21 |
Correct |
4 ms |
7380 KB |
Output is correct |
22 |
Correct |
4 ms |
7508 KB |
Output is correct |
23 |
Correct |
4 ms |
7508 KB |
Output is correct |
24 |
Correct |
4 ms |
7484 KB |
Output is correct |
25 |
Correct |
4 ms |
7380 KB |
Output is correct |
26 |
Correct |
4 ms |
7388 KB |
Output is correct |
27 |
Correct |
5 ms |
7396 KB |
Output is correct |
28 |
Correct |
4 ms |
7508 KB |
Output is correct |
29 |
Correct |
4 ms |
7380 KB |
Output is correct |
30 |
Correct |
4 ms |
7384 KB |
Output is correct |
31 |
Correct |
5 ms |
7508 KB |
Output is correct |
32 |
Correct |
4 ms |
7380 KB |
Output is correct |
33 |
Correct |
3 ms |
7380 KB |
Output is correct |
34 |
Correct |
4 ms |
7380 KB |
Output is correct |
35 |
Correct |
3 ms |
7380 KB |
Output is correct |
36 |
Correct |
5 ms |
7380 KB |
Output is correct |
37 |
Correct |
4 ms |
7384 KB |
Output is correct |
38 |
Correct |
4 ms |
7380 KB |
Output is correct |
39 |
Correct |
4 ms |
7380 KB |
Output is correct |
40 |
Correct |
4 ms |
7384 KB |
Output is correct |
41 |
Correct |
4 ms |
7380 KB |
Output is correct |
42 |
Correct |
4 ms |
7380 KB |
Output is correct |
43 |
Correct |
4 ms |
7380 KB |
Output is correct |
44 |
Correct |
4 ms |
7376 KB |
Output is correct |
45 |
Correct |
5 ms |
7376 KB |
Output is correct |
46 |
Correct |
4 ms |
7380 KB |
Output is correct |
47 |
Correct |
5 ms |
7380 KB |
Output is correct |
48 |
Correct |
4 ms |
7380 KB |
Output is correct |
49 |
Correct |
4 ms |
7380 KB |
Output is correct |
50 |
Correct |
3 ms |
7380 KB |
Output is correct |
51 |
Correct |
4 ms |
7388 KB |
Output is correct |
52 |
Correct |
4 ms |
7380 KB |
Output is correct |
53 |
Correct |
4 ms |
7380 KB |
Output is correct |
54 |
Correct |
4 ms |
7288 KB |
Output is correct |
55 |
Correct |
3 ms |
7380 KB |
Output is correct |
56 |
Correct |
6 ms |
7340 KB |
Output is correct |
57 |
Correct |
4 ms |
7380 KB |
Output is correct |
58 |
Correct |
4 ms |
7520 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
4 ms |
7380 KB |
Output is correct |
2 |
Correct |
4 ms |
7380 KB |
Output is correct |
3 |
Correct |
4 ms |
7380 KB |
Output is correct |
4 |
Correct |
4 ms |
7320 KB |
Output is correct |
5 |
Correct |
4 ms |
7380 KB |
Output is correct |
6 |
Correct |
4 ms |
7380 KB |
Output is correct |
7 |
Correct |
4 ms |
7380 KB |
Output is correct |
8 |
Correct |
4 ms |
7252 KB |
Output is correct |
9 |
Correct |
4 ms |
7252 KB |
Output is correct |
10 |
Correct |
4 ms |
7380 KB |
Output is correct |
11 |
Correct |
4 ms |
7380 KB |
Output is correct |
12 |
Correct |
4 ms |
7380 KB |
Output is correct |
13 |
Correct |
4 ms |
7380 KB |
Output is correct |
14 |
Correct |
4 ms |
7380 KB |
Output is correct |
15 |
Correct |
4 ms |
7380 KB |
Output is correct |
16 |
Correct |
4 ms |
7376 KB |
Output is correct |
17 |
Correct |
4 ms |
7380 KB |
Output is correct |
18 |
Correct |
4 ms |
7388 KB |
Output is correct |
19 |
Correct |
3 ms |
7276 KB |
Output is correct |
20 |
Correct |
4 ms |
7384 KB |
Output is correct |
21 |
Correct |
4 ms |
7380 KB |
Output is correct |
22 |
Correct |
4 ms |
7508 KB |
Output is correct |
23 |
Correct |
4 ms |
7508 KB |
Output is correct |
24 |
Correct |
4 ms |
7484 KB |
Output is correct |
25 |
Correct |
4 ms |
7380 KB |
Output is correct |
26 |
Correct |
4 ms |
7388 KB |
Output is correct |
27 |
Correct |
5 ms |
7396 KB |
Output is correct |
28 |
Correct |
4 ms |
7508 KB |
Output is correct |
29 |
Correct |
4 ms |
7380 KB |
Output is correct |
30 |
Correct |
4 ms |
7384 KB |
Output is correct |
31 |
Correct |
5 ms |
7508 KB |
Output is correct |
32 |
Correct |
4 ms |
7380 KB |
Output is correct |
33 |
Correct |
3 ms |
7380 KB |
Output is correct |
34 |
Correct |
4 ms |
7380 KB |
Output is correct |
35 |
Correct |
3 ms |
7380 KB |
Output is correct |
36 |
Correct |
5 ms |
7380 KB |
Output is correct |
37 |
Correct |
4 ms |
7384 KB |
Output is correct |
38 |
Correct |
4 ms |
7380 KB |
Output is correct |
39 |
Correct |
4 ms |
7380 KB |
Output is correct |
40 |
Correct |
4 ms |
7384 KB |
Output is correct |
41 |
Correct |
4 ms |
7380 KB |
Output is correct |
42 |
Correct |
4 ms |
7380 KB |
Output is correct |
43 |
Correct |
4 ms |
7380 KB |
Output is correct |
44 |
Correct |
4 ms |
7376 KB |
Output is correct |
45 |
Correct |
5 ms |
7376 KB |
Output is correct |
46 |
Correct |
4 ms |
7380 KB |
Output is correct |
47 |
Correct |
5 ms |
7380 KB |
Output is correct |
48 |
Correct |
4 ms |
7380 KB |
Output is correct |
49 |
Correct |
4 ms |
7380 KB |
Output is correct |
50 |
Correct |
3 ms |
7380 KB |
Output is correct |
51 |
Correct |
4 ms |
7388 KB |
Output is correct |
52 |
Correct |
4 ms |
7380 KB |
Output is correct |
53 |
Correct |
4 ms |
7380 KB |
Output is correct |
54 |
Correct |
4 ms |
7288 KB |
Output is correct |
55 |
Correct |
3 ms |
7380 KB |
Output is correct |
56 |
Correct |
6 ms |
7340 KB |
Output is correct |
57 |
Correct |
4 ms |
7380 KB |
Output is correct |
58 |
Correct |
4 ms |
7520 KB |
Output is correct |
59 |
Runtime error |
10 ms |
14804 KB |
Execution killed with signal 11 |
60 |
Halted |
0 ms |
0 KB |
- |