#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define fi first
#define se second
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxN = 1e6 + 5;
const int mod = 1e9 + 7;
const ll oo = 1e18;
int n;
vector<int> adj[maxN];
int depth[maxN];
void ReadInput()
{
cin >> n;
for(int i=1; i<n; i++)
{
int u, v;
cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
}
void dfs(int u, int par)
{
for(int v : adj[u])
{
if(v == par) continue;
depth[v] = depth[u] + 1;
dfs(v, u);
}
}
void Solve()
{
dfs(n, 0);
vector<int> leaf;
for(int i=1; i<=n; i++)
{
if(adj[i].size() == 1) leaf.pb(i);
}
sort(leaf.begin(), leaf.end(), [](int i, int j)
{
return depth[i] < depth[j];
});
int l = 0, step = leaf.size() / 2;
if(leaf.size() % 2 == 0)
{
cout << leaf.size() / 2 << '\n';
while(l + step < leaf.size())
{
cout << leaf[l] << " " << leaf[l + step] << '\n';
l++;
}
return;
}
cout << leaf.size() / 2 + 1 << '\n';
while(l + step < leaf.size() - 1)
{
cout << leaf[l] << " " << leaf[l + step] << '\n';
l++;
}
cout << leaf.back() << " " << leaf[0];
}
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
ReadInput();
Solve();
}
Compilation message
net.cpp: In function 'void Solve()':
net.cpp:54:24: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
54 | while(l + step < leaf.size())
| ~~~~~~~~~^~~~~~~~~~~~~
net.cpp:62:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
62 | while(l + step < leaf.size() - 1)
| ~~~~~~~~~^~~~~~~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
12 ms |
23764 KB |
Output is correct |
2 |
Correct |
12 ms |
23764 KB |
Output is correct |
3 |
Correct |
13 ms |
23812 KB |
Output is correct |
4 |
Correct |
13 ms |
23796 KB |
Output is correct |
5 |
Correct |
13 ms |
23720 KB |
Output is correct |
6 |
Correct |
13 ms |
23816 KB |
Output is correct |
7 |
Correct |
16 ms |
23824 KB |
Output is correct |
8 |
Correct |
14 ms |
23884 KB |
Output is correct |
9 |
Correct |
12 ms |
23764 KB |
Output is correct |
10 |
Incorrect |
13 ms |
23736 KB |
Breaking single line is causing network to disconnect. |
11 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
12 ms |
23764 KB |
Output is correct |
2 |
Correct |
12 ms |
23764 KB |
Output is correct |
3 |
Correct |
13 ms |
23812 KB |
Output is correct |
4 |
Correct |
13 ms |
23796 KB |
Output is correct |
5 |
Correct |
13 ms |
23720 KB |
Output is correct |
6 |
Correct |
13 ms |
23816 KB |
Output is correct |
7 |
Correct |
16 ms |
23824 KB |
Output is correct |
8 |
Correct |
14 ms |
23884 KB |
Output is correct |
9 |
Correct |
12 ms |
23764 KB |
Output is correct |
10 |
Incorrect |
13 ms |
23736 KB |
Breaking single line is causing network to disconnect. |
11 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
12 ms |
23764 KB |
Output is correct |
2 |
Correct |
12 ms |
23764 KB |
Output is correct |
3 |
Correct |
13 ms |
23812 KB |
Output is correct |
4 |
Correct |
13 ms |
23796 KB |
Output is correct |
5 |
Correct |
13 ms |
23720 KB |
Output is correct |
6 |
Correct |
13 ms |
23816 KB |
Output is correct |
7 |
Correct |
16 ms |
23824 KB |
Output is correct |
8 |
Correct |
14 ms |
23884 KB |
Output is correct |
9 |
Correct |
12 ms |
23764 KB |
Output is correct |
10 |
Incorrect |
13 ms |
23736 KB |
Breaking single line is causing network to disconnect. |
11 |
Halted |
0 ms |
0 KB |
- |