#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define endl '\n'
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int N = 1e5 + 50;
int n, sub[N], k, par[N], t;
vector<int> adj[N];
vector<int> vc[N];
set<pii> st;
vector<pii> out;
void dfs(int u, int p) {
par[u] = p;
for (int v:adj[u]) {
if (v == p) continue;
dfs(v, u);
sub[u] += sub[v];
}
}
void dfs2(int u, int p) {
if (adj[u].size() == 1) {
vc[t].push_back(u);
}
for (int v:adj[u]) {
if (v == p) continue;
dfs2(v, u);
}
}
void solve() {
cin >> n;
for (int i = 1; i <= n-1; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for (int u = 1; u <= n; u++) {
if (adj[u].size() == 1) {
k++;
sub[u] = 1;
}
}
dfs(1, 0);
int r = 0;
for (int u = 1; u <= n; u++) {
if (adj[u].size() == 1) continue;
bool flg = 1;
for (int v:adj[u]) {
if (v == par[u]) flg = flg&&(k-sub[u] <= k/2);
else flg = flg&&(sub[v] <= k/2);
}
if (flg) {
r = u;
break;
}
}
for (int u:adj[r]) {
t++;
dfs2(u, r);
}
for (int i = 1; i <= t; i++) {
st.insert({-vc[i].size(), i});
}
while (st.size() >= 2) {
auto it = st.begin();
int A = it->S; it++;
int B = it->S;
out.push_back({vc[A].back(), vc[B].back()});
st.erase({-vc[A].size(), A});
st.erase({-vc[B].size(), B});
vc[A].pop_back();
vc[B].pop_back();
if (!vc[A].empty()) st.insert({-vc[A].size(), A});
if (!vc[B].empty()) st.insert({-vc[B].size(), B});
}
if (st.size()) {
int A = st.begin()->S;
int u = vc[A].back();
out.push_back({u, r});
}
cout << out.size() << endl;
for (pii x:out) {
cout << x.F << ' ' << x.S << endl;
}
}
int main() {
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
solve();
return 0;
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
4948 KB |
Output is correct |
2 |
Correct |
4 ms |
4948 KB |
Output is correct |
3 |
Correct |
3 ms |
4948 KB |
Output is correct |
4 |
Correct |
3 ms |
4948 KB |
Output is correct |
5 |
Correct |
3 ms |
4912 KB |
Output is correct |
6 |
Correct |
3 ms |
4948 KB |
Output is correct |
7 |
Correct |
3 ms |
5024 KB |
Output is correct |
8 |
Correct |
2 ms |
4948 KB |
Output is correct |
9 |
Correct |
3 ms |
4948 KB |
Output is correct |
10 |
Correct |
2 ms |
4948 KB |
Output is correct |
11 |
Correct |
2 ms |
5024 KB |
Output is correct |
12 |
Correct |
3 ms |
4948 KB |
Output is correct |
13 |
Correct |
3 ms |
5028 KB |
Output is correct |
14 |
Correct |
3 ms |
4948 KB |
Output is correct |
15 |
Correct |
3 ms |
4948 KB |
Output is correct |
16 |
Correct |
3 ms |
4948 KB |
Output is correct |
17 |
Correct |
3 ms |
5024 KB |
Output is correct |
18 |
Correct |
4 ms |
4948 KB |
Output is correct |
19 |
Correct |
3 ms |
5024 KB |
Output is correct |
20 |
Correct |
3 ms |
5024 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
4948 KB |
Output is correct |
2 |
Correct |
4 ms |
4948 KB |
Output is correct |
3 |
Correct |
3 ms |
4948 KB |
Output is correct |
4 |
Correct |
3 ms |
4948 KB |
Output is correct |
5 |
Correct |
3 ms |
4912 KB |
Output is correct |
6 |
Correct |
3 ms |
4948 KB |
Output is correct |
7 |
Correct |
3 ms |
5024 KB |
Output is correct |
8 |
Correct |
2 ms |
4948 KB |
Output is correct |
9 |
Correct |
3 ms |
4948 KB |
Output is correct |
10 |
Correct |
2 ms |
4948 KB |
Output is correct |
11 |
Correct |
2 ms |
5024 KB |
Output is correct |
12 |
Correct |
3 ms |
4948 KB |
Output is correct |
13 |
Correct |
3 ms |
5028 KB |
Output is correct |
14 |
Correct |
3 ms |
4948 KB |
Output is correct |
15 |
Correct |
3 ms |
4948 KB |
Output is correct |
16 |
Correct |
3 ms |
4948 KB |
Output is correct |
17 |
Correct |
3 ms |
5024 KB |
Output is correct |
18 |
Correct |
4 ms |
4948 KB |
Output is correct |
19 |
Correct |
3 ms |
5024 KB |
Output is correct |
20 |
Correct |
3 ms |
5024 KB |
Output is correct |
21 |
Correct |
3 ms |
4948 KB |
Output is correct |
22 |
Correct |
8 ms |
5212 KB |
Output is correct |
23 |
Correct |
4 ms |
5160 KB |
Output is correct |
24 |
Correct |
4 ms |
5204 KB |
Output is correct |
25 |
Correct |
4 ms |
5148 KB |
Output is correct |
26 |
Correct |
4 ms |
5076 KB |
Output is correct |
27 |
Correct |
4 ms |
5080 KB |
Output is correct |
28 |
Correct |
8 ms |
5036 KB |
Output is correct |
29 |
Correct |
4 ms |
5076 KB |
Output is correct |
30 |
Correct |
3 ms |
4948 KB |
Output is correct |
31 |
Correct |
4 ms |
5096 KB |
Output is correct |
32 |
Correct |
3 ms |
4948 KB |
Output is correct |
33 |
Correct |
3 ms |
4948 KB |
Output is correct |
34 |
Correct |
3 ms |
4948 KB |
Output is correct |
35 |
Correct |
4 ms |
5024 KB |
Output is correct |
36 |
Correct |
4 ms |
4952 KB |
Output is correct |
37 |
Correct |
9 ms |
5076 KB |
Output is correct |
38 |
Correct |
10 ms |
5076 KB |
Output is correct |
39 |
Correct |
8 ms |
4952 KB |
Output is correct |
40 |
Correct |
3 ms |
5024 KB |
Output is correct |
41 |
Correct |
3 ms |
4948 KB |
Output is correct |
42 |
Correct |
4 ms |
5020 KB |
Output is correct |
43 |
Correct |
3 ms |
5160 KB |
Output is correct |
44 |
Correct |
3 ms |
5028 KB |
Output is correct |
45 |
Correct |
3 ms |
4948 KB |
Output is correct |
46 |
Correct |
4 ms |
5028 KB |
Output is correct |
47 |
Correct |
3 ms |
4948 KB |
Output is correct |
48 |
Correct |
3 ms |
4948 KB |
Output is correct |
49 |
Correct |
5 ms |
5036 KB |
Output is correct |
50 |
Correct |
5 ms |
5024 KB |
Output is correct |
51 |
Correct |
3 ms |
4948 KB |
Output is correct |
52 |
Correct |
3 ms |
4948 KB |
Output is correct |
53 |
Correct |
3 ms |
5076 KB |
Output is correct |
54 |
Correct |
4 ms |
4940 KB |
Output is correct |
55 |
Correct |
3 ms |
5072 KB |
Output is correct |
56 |
Correct |
3 ms |
5024 KB |
Output is correct |
57 |
Correct |
3 ms |
5076 KB |
Output is correct |
58 |
Correct |
4 ms |
5076 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
4948 KB |
Output is correct |
2 |
Correct |
4 ms |
4948 KB |
Output is correct |
3 |
Correct |
3 ms |
4948 KB |
Output is correct |
4 |
Correct |
3 ms |
4948 KB |
Output is correct |
5 |
Correct |
3 ms |
4912 KB |
Output is correct |
6 |
Correct |
3 ms |
4948 KB |
Output is correct |
7 |
Correct |
3 ms |
5024 KB |
Output is correct |
8 |
Correct |
2 ms |
4948 KB |
Output is correct |
9 |
Correct |
3 ms |
4948 KB |
Output is correct |
10 |
Correct |
2 ms |
4948 KB |
Output is correct |
11 |
Correct |
2 ms |
5024 KB |
Output is correct |
12 |
Correct |
3 ms |
4948 KB |
Output is correct |
13 |
Correct |
3 ms |
5028 KB |
Output is correct |
14 |
Correct |
3 ms |
4948 KB |
Output is correct |
15 |
Correct |
3 ms |
4948 KB |
Output is correct |
16 |
Correct |
3 ms |
4948 KB |
Output is correct |
17 |
Correct |
3 ms |
5024 KB |
Output is correct |
18 |
Correct |
4 ms |
4948 KB |
Output is correct |
19 |
Correct |
3 ms |
5024 KB |
Output is correct |
20 |
Correct |
3 ms |
5024 KB |
Output is correct |
21 |
Correct |
3 ms |
4948 KB |
Output is correct |
22 |
Correct |
8 ms |
5212 KB |
Output is correct |
23 |
Correct |
4 ms |
5160 KB |
Output is correct |
24 |
Correct |
4 ms |
5204 KB |
Output is correct |
25 |
Correct |
4 ms |
5148 KB |
Output is correct |
26 |
Correct |
4 ms |
5076 KB |
Output is correct |
27 |
Correct |
4 ms |
5080 KB |
Output is correct |
28 |
Correct |
8 ms |
5036 KB |
Output is correct |
29 |
Correct |
4 ms |
5076 KB |
Output is correct |
30 |
Correct |
3 ms |
4948 KB |
Output is correct |
31 |
Correct |
4 ms |
5096 KB |
Output is correct |
32 |
Correct |
3 ms |
4948 KB |
Output is correct |
33 |
Correct |
3 ms |
4948 KB |
Output is correct |
34 |
Correct |
3 ms |
4948 KB |
Output is correct |
35 |
Correct |
4 ms |
5024 KB |
Output is correct |
36 |
Correct |
4 ms |
4952 KB |
Output is correct |
37 |
Correct |
9 ms |
5076 KB |
Output is correct |
38 |
Correct |
10 ms |
5076 KB |
Output is correct |
39 |
Correct |
8 ms |
4952 KB |
Output is correct |
40 |
Correct |
3 ms |
5024 KB |
Output is correct |
41 |
Correct |
3 ms |
4948 KB |
Output is correct |
42 |
Correct |
4 ms |
5020 KB |
Output is correct |
43 |
Correct |
3 ms |
5160 KB |
Output is correct |
44 |
Correct |
3 ms |
5028 KB |
Output is correct |
45 |
Correct |
3 ms |
4948 KB |
Output is correct |
46 |
Correct |
4 ms |
5028 KB |
Output is correct |
47 |
Correct |
3 ms |
4948 KB |
Output is correct |
48 |
Correct |
3 ms |
4948 KB |
Output is correct |
49 |
Correct |
5 ms |
5036 KB |
Output is correct |
50 |
Correct |
5 ms |
5024 KB |
Output is correct |
51 |
Correct |
3 ms |
4948 KB |
Output is correct |
52 |
Correct |
3 ms |
4948 KB |
Output is correct |
53 |
Correct |
3 ms |
5076 KB |
Output is correct |
54 |
Correct |
4 ms |
4940 KB |
Output is correct |
55 |
Correct |
3 ms |
5072 KB |
Output is correct |
56 |
Correct |
3 ms |
5024 KB |
Output is correct |
57 |
Correct |
3 ms |
5076 KB |
Output is correct |
58 |
Correct |
4 ms |
5076 KB |
Output is correct |
59 |
Runtime error |
8 ms |
9940 KB |
Execution killed with signal 11 |
60 |
Halted |
0 ms |
0 KB |
- |