# |
Submission time |
Handle |
Problem |
Language |
Result |
Execution time |
Memory |
928630 |
2024-02-16T21:04:49 Z |
Regulus |
Network (BOI15_net) |
C++17 |
|
1 ms |
2972 KB |
#include <bits/stdc++.h>
#define IO ios::sync_with_stdio(false);cin.tie(0);
#define debug(x) cerr << #x << " = " << (x) << ' '
#define bug(x) cerr << (x) << ' '
#define endl cerr << '\n'
#define all(v) (v).begin(), (v).end()
#define SZ(v) (ll)(v).size()
#define lowbit(x) (x)&-(x)
#define pb emplace_back
#define F first
#define S second
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
const int N = 1e5+5;
int sz[N], cnt, pos, mxs[N];
vector<int> g[N], vec, pre;
vector<pll> ans;
inline void dfs(int x, int fa)
{
if (SZ(g[x]) == 1) sz[x] = 1;
for (int v : g[x])
{
if (v == fa) continue;
dfs(v, x), sz[x] += sz[v];
mxs[x] = max(mxs[x], sz[v]);
}
mxs[x] = max(mxs[x], cnt-sz[x]);
if (mxs[x] < mxs[pos]) pos = x;
}
inline void dfs2(int x, int fa)
{
if (SZ(g[x]) == 1) vec.pb(x);
for (int v : g[x]) if (v != fa) dfs2(v, x);
}
int main(void)
{ IO
int n, i;
cin >> n;
for (i=0; i < n-1; ++i)
{ int x, y; cin >> x >> y, g[x].pb(y), g[y].pb(x); }
for (i=1; i <= n; ++i) if (SZ(g[i]) == 1) ++cnt;
pos = 0, mxs[0] = 2e9;
dfs(1, 0);
//debug(pos), endl;
for (int v : g[pos])
{
dfs2(v, pos);
while (!pre.empty() && !vec.empty())
{
ans.pb(pre.back(), vec.back());
pre.pop_back(); vec.pop_back();
}
while (!vec.empty()) pre.pb(vec.back()), vec.pop_back();
}
for (int x : pre) ans.pb(x, pos);
cout << SZ(ans) << '\n';
for (auto p : ans) cout << p.F << ' ' << p.S << '\n';
return 0;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
2652 KB |
Output is correct |
2 |
Incorrect |
1 ms |
2972 KB |
Invalid number of links. |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
2652 KB |
Output is correct |
2 |
Incorrect |
1 ms |
2972 KB |
Invalid number of links. |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
2652 KB |
Output is correct |
2 |
Incorrect |
1 ms |
2972 KB |
Invalid number of links. |
3 |
Halted |
0 ms |
0 KB |
- |