| # |
Submission time |
Handle |
Problem |
Language |
Result |
Execution time |
Memory |
| 931766 |
2024-02-22T10:41:30 Z |
vjudge1 |
Network (BOI15_net) |
C++17 |
|
1 ms |
428 KB |
#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
using namespace std;
const int N = 2000 + 10, LG = 20;
int n, h[N], par[N][LG];
bool mark[N];
vector<int> G[N], vec;
vector<pair<int, pair<int, int>>> vec1;
void dfs(int v = 1, int p = 0) {
par[v][0] = p;
if (G[v].size() == 1) vec.pb(v);
for (auto e : G[v])
if (e ^ p) {
h[e] = h[v] + 1;
dfs(e, v);
}
}
int lca(int u, int v) {
if (u == v) return u;
if (h[u] < h[v]) swap(u, v);
int k = h[u] - h[v];
for (int lg = 0; lg < LG; lg++)
if (k & (1 << lg)) u = par[u][lg];
if (u == v) return v;
for (int lg = LG - 1; lg >= 0; lg--)
if (par[u][lg] != par[v][lg]) u = par[u][lg], v = par[v][lg];
return par[u][0];
}
int main() {
ios:: sync_with_stdio(0), cin.tie(0);
cin >> n;
for (int i = 0; i < n - 1; i++) {
int u, v;
cin >> u >> v;
G[u].pb(v);
G[v].pb(u);
}
dfs();
for (int lg = 1; lg < LG; lg++)
for (int i = 1; i <= n; i++)
par[i][lg] = par[par[i][lg - 1]][lg - 1];
for (int i = 0; i < (int)vec.size(); i++)
for (int j = i + 1; j < (int)vec.size(); j++) {
int l = lca(vec[i], vec[j]);
vec1.pb({h[vec[i]] + h[vec[j]] - 2 * h[l], {vec[i], vec[j]}});
}
sort(vec1.begin(), vec1.end());
reverse(vec1.begin(), vec1.end());
cout << ((int)vec.size() + 1) / 2 << endl;
int cnt = 0;
for (auto e : vec1) {
if (cnt == (int) vec.size()) return 0;
if (!mark[e.S.F] && !mark[e.S.S]) {
cout << e.S.F << ' ' << e.S.S << endl;
mark[e.S.F] = mark[e.S.S] = true, cnt += 2;
}
else if ((int)vec.size() & 1)
if (cnt + 1 == (int)vec.size()) {
if (!mark[e.S.S]) return cout << vec1[0].S.F << ' ' << e.S.S << endl, 0;
else if (!mark[e.S.F]) return cout << vec1[0].S.F << ' ' << e.S.F << endl, 0;
}
}
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 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 |
0 ms |
348 KB |
Output is correct |
| 6 |
Correct |
0 ms |
348 KB |
Output is correct |
| 7 |
Correct |
1 ms |
348 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
1 ms |
344 KB |
Output is correct |
| 11 |
Correct |
1 ms |
348 KB |
Output is correct |
| 12 |
Correct |
0 ms |
428 KB |
Output is correct |
| 13 |
Correct |
1 ms |
344 KB |
Output is correct |
| 14 |
Correct |
0 ms |
348 KB |
Output is correct |
| 15 |
Correct |
1 ms |
348 KB |
Output is correct |
| 16 |
Correct |
0 ms |
344 KB |
Output is correct |
| 17 |
Correct |
0 ms |
348 KB |
Output is correct |
| 18 |
Incorrect |
0 ms |
348 KB |
Breaking single line is causing network to disconnect. |
| 19 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 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 |
0 ms |
348 KB |
Output is correct |
| 6 |
Correct |
0 ms |
348 KB |
Output is correct |
| 7 |
Correct |
1 ms |
348 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
1 ms |
344 KB |
Output is correct |
| 11 |
Correct |
1 ms |
348 KB |
Output is correct |
| 12 |
Correct |
0 ms |
428 KB |
Output is correct |
| 13 |
Correct |
1 ms |
344 KB |
Output is correct |
| 14 |
Correct |
0 ms |
348 KB |
Output is correct |
| 15 |
Correct |
1 ms |
348 KB |
Output is correct |
| 16 |
Correct |
0 ms |
344 KB |
Output is correct |
| 17 |
Correct |
0 ms |
348 KB |
Output is correct |
| 18 |
Incorrect |
0 ms |
348 KB |
Breaking single line is causing network to disconnect. |
| 19 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 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 |
0 ms |
348 KB |
Output is correct |
| 6 |
Correct |
0 ms |
348 KB |
Output is correct |
| 7 |
Correct |
1 ms |
348 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
348 KB |
Output is correct |
| 10 |
Correct |
1 ms |
344 KB |
Output is correct |
| 11 |
Correct |
1 ms |
348 KB |
Output is correct |
| 12 |
Correct |
0 ms |
428 KB |
Output is correct |
| 13 |
Correct |
1 ms |
344 KB |
Output is correct |
| 14 |
Correct |
0 ms |
348 KB |
Output is correct |
| 15 |
Correct |
1 ms |
348 KB |
Output is correct |
| 16 |
Correct |
0 ms |
344 KB |
Output is correct |
| 17 |
Correct |
0 ms |
348 KB |
Output is correct |
| 18 |
Incorrect |
0 ms |
348 KB |
Breaking single line is causing network to disconnect. |
| 19 |
Halted |
0 ms |
0 KB |
- |
