#include <bits/stdc++.h>
#define se second
#define fs first
#define mp make_pair
#define pb push_back
#define ll long long
#define ii pair<ll,ll>
#define ld long double
#define SZ(v) (int)v.size()
#define ALL(v) v.begin(), v.end()
#define bit(msk, i) ((msk >> i) & 1)
#define iter(id, v) for(auto id : v)
#define rep(i,m,n) for(int i=(m); i<=(n); i++)
#define reb(i,m,n) for(int i=(m); i>=(n); i--)
using namespace std;
mt19937_64 rd(chrono :: steady_clock :: now().time_since_epoch().count());
ll Rand(ll l, ll r) { return uniform_int_distribution<ll> (l, r)(rd); }
const int N = 5e5 + 7;
const int Mod = 998244353;
const int szBL = 916;
const ll INF = 1e18;
const int BASE = 137;
int n;
vector<int> ke[N];
int in[N], out[N];
vector<pair<int,int>> Ans;
vector<int> dfs (int u, int p) {
if (SZ(ke[u]) == 1) return vector<int> (1, u);
vector<int> prv;
iter (&v, ke[u]) {
if (v == p) continue;
vector<int> cur = dfs (v, u);
if (SZ(cur) > SZ(prv)) swap(cur, prv);
while (SZ(prv) + SZ(cur) > 2 && cur.size()) {
Ans.push_back(mp(cur.back(), prv.back()));
cur.pop_back();
prv.pop_back();
}
iter (&id, cur) prv.push_back(id);
}
return prv;
}
void solution () {
cin >> n;
rep (i, 1, n - 1) {
int u, v;
cin >> u >> v;
ke[u].push_back(v);
ke[v].push_back(u);
}
int root = 1;
rep (i, 1, n) if (SZ(ke[i]) > 1) root = i;
vector<int> cur = dfs (root, 0);
if (SZ(cur) == 1) cur.push_back(root);
Ans.push_back(mp(cur[0], cur[1]));
cout << SZ(Ans) <<"\n";
iter (&id, Ans) cout << id.fs<< " "<<id.se <<"\n";
}
#define file(name) freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout);
int main () {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
// file ("fbuy");
int num_Test = 1;
// cin >> num_Test;
while (num_Test--)
solution();
}
/*
7
1 2 4
2 3 12
3 4 2
4 5 48
5 6 2
6 7 123
*/
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
13660 KB |
Output is correct |
2 |
Correct |
2 ms |
13660 KB |
Output is correct |
3 |
Correct |
2 ms |
13660 KB |
Output is correct |
4 |
Correct |
4 ms |
13660 KB |
Output is correct |
5 |
Correct |
2 ms |
13660 KB |
Output is correct |
6 |
Correct |
3 ms |
13656 KB |
Output is correct |
7 |
Correct |
3 ms |
13660 KB |
Output is correct |
8 |
Correct |
2 ms |
13880 KB |
Output is correct |
9 |
Correct |
3 ms |
13656 KB |
Output is correct |
10 |
Correct |
2 ms |
13660 KB |
Output is correct |
11 |
Correct |
2 ms |
13888 KB |
Output is correct |
12 |
Correct |
2 ms |
13660 KB |
Output is correct |
13 |
Correct |
3 ms |
13660 KB |
Output is correct |
14 |
Correct |
3 ms |
13660 KB |
Output is correct |
15 |
Correct |
2 ms |
13660 KB |
Output is correct |
16 |
Correct |
3 ms |
13656 KB |
Output is correct |
17 |
Correct |
4 ms |
13660 KB |
Output is correct |
18 |
Correct |
3 ms |
13656 KB |
Output is correct |
19 |
Correct |
3 ms |
13656 KB |
Output is correct |
20 |
Correct |
3 ms |
13656 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
13660 KB |
Output is correct |
2 |
Correct |
2 ms |
13660 KB |
Output is correct |
3 |
Correct |
2 ms |
13660 KB |
Output is correct |
4 |
Correct |
4 ms |
13660 KB |
Output is correct |
5 |
Correct |
2 ms |
13660 KB |
Output is correct |
6 |
Correct |
3 ms |
13656 KB |
Output is correct |
7 |
Correct |
3 ms |
13660 KB |
Output is correct |
8 |
Correct |
2 ms |
13880 KB |
Output is correct |
9 |
Correct |
3 ms |
13656 KB |
Output is correct |
10 |
Correct |
2 ms |
13660 KB |
Output is correct |
11 |
Correct |
2 ms |
13888 KB |
Output is correct |
12 |
Correct |
2 ms |
13660 KB |
Output is correct |
13 |
Correct |
3 ms |
13660 KB |
Output is correct |
14 |
Correct |
3 ms |
13660 KB |
Output is correct |
15 |
Correct |
2 ms |
13660 KB |
Output is correct |
16 |
Correct |
3 ms |
13656 KB |
Output is correct |
17 |
Correct |
4 ms |
13660 KB |
Output is correct |
18 |
Correct |
3 ms |
13656 KB |
Output is correct |
19 |
Correct |
3 ms |
13656 KB |
Output is correct |
20 |
Correct |
3 ms |
13656 KB |
Output is correct |
21 |
Correct |
3 ms |
13660 KB |
Output is correct |
22 |
Correct |
3 ms |
13916 KB |
Output is correct |
23 |
Correct |
3 ms |
13912 KB |
Output is correct |
24 |
Correct |
3 ms |
13916 KB |
Output is correct |
25 |
Correct |
3 ms |
13916 KB |
Output is correct |
26 |
Correct |
2 ms |
13916 KB |
Output is correct |
27 |
Correct |
4 ms |
13916 KB |
Output is correct |
28 |
Correct |
3 ms |
13916 KB |
Output is correct |
29 |
Correct |
3 ms |
13916 KB |
Output is correct |
30 |
Correct |
2 ms |
13656 KB |
Output is correct |
31 |
Correct |
3 ms |
13916 KB |
Output is correct |
32 |
Correct |
2 ms |
13660 KB |
Output is correct |
33 |
Correct |
3 ms |
13656 KB |
Output is correct |
34 |
Correct |
2 ms |
13660 KB |
Output is correct |
35 |
Correct |
2 ms |
13660 KB |
Output is correct |
36 |
Correct |
3 ms |
13816 KB |
Output is correct |
37 |
Correct |
3 ms |
13916 KB |
Output is correct |
38 |
Correct |
3 ms |
13888 KB |
Output is correct |
39 |
Correct |
2 ms |
13912 KB |
Output is correct |
40 |
Correct |
2 ms |
13660 KB |
Output is correct |
41 |
Correct |
2 ms |
13660 KB |
Output is correct |
42 |
Correct |
2 ms |
13752 KB |
Output is correct |
43 |
Correct |
3 ms |
13912 KB |
Output is correct |
44 |
Correct |
2 ms |
13660 KB |
Output is correct |
45 |
Correct |
2 ms |
13660 KB |
Output is correct |
46 |
Correct |
3 ms |
13916 KB |
Output is correct |
47 |
Correct |
3 ms |
13660 KB |
Output is correct |
48 |
Correct |
2 ms |
13660 KB |
Output is correct |
49 |
Correct |
2 ms |
13916 KB |
Output is correct |
50 |
Correct |
2 ms |
13656 KB |
Output is correct |
51 |
Correct |
2 ms |
13656 KB |
Output is correct |
52 |
Correct |
2 ms |
13916 KB |
Output is correct |
53 |
Correct |
2 ms |
13916 KB |
Output is correct |
54 |
Correct |
2 ms |
13660 KB |
Output is correct |
55 |
Correct |
3 ms |
13660 KB |
Output is correct |
56 |
Correct |
2 ms |
13660 KB |
Output is correct |
57 |
Correct |
2 ms |
13916 KB |
Output is correct |
58 |
Correct |
3 ms |
13916 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
2 ms |
13660 KB |
Output is correct |
2 |
Correct |
2 ms |
13660 KB |
Output is correct |
3 |
Correct |
2 ms |
13660 KB |
Output is correct |
4 |
Correct |
4 ms |
13660 KB |
Output is correct |
5 |
Correct |
2 ms |
13660 KB |
Output is correct |
6 |
Correct |
3 ms |
13656 KB |
Output is correct |
7 |
Correct |
3 ms |
13660 KB |
Output is correct |
8 |
Correct |
2 ms |
13880 KB |
Output is correct |
9 |
Correct |
3 ms |
13656 KB |
Output is correct |
10 |
Correct |
2 ms |
13660 KB |
Output is correct |
11 |
Correct |
2 ms |
13888 KB |
Output is correct |
12 |
Correct |
2 ms |
13660 KB |
Output is correct |
13 |
Correct |
3 ms |
13660 KB |
Output is correct |
14 |
Correct |
3 ms |
13660 KB |
Output is correct |
15 |
Correct |
2 ms |
13660 KB |
Output is correct |
16 |
Correct |
3 ms |
13656 KB |
Output is correct |
17 |
Correct |
4 ms |
13660 KB |
Output is correct |
18 |
Correct |
3 ms |
13656 KB |
Output is correct |
19 |
Correct |
3 ms |
13656 KB |
Output is correct |
20 |
Correct |
3 ms |
13656 KB |
Output is correct |
21 |
Correct |
3 ms |
13660 KB |
Output is correct |
22 |
Correct |
3 ms |
13916 KB |
Output is correct |
23 |
Correct |
3 ms |
13912 KB |
Output is correct |
24 |
Correct |
3 ms |
13916 KB |
Output is correct |
25 |
Correct |
3 ms |
13916 KB |
Output is correct |
26 |
Correct |
2 ms |
13916 KB |
Output is correct |
27 |
Correct |
4 ms |
13916 KB |
Output is correct |
28 |
Correct |
3 ms |
13916 KB |
Output is correct |
29 |
Correct |
3 ms |
13916 KB |
Output is correct |
30 |
Correct |
2 ms |
13656 KB |
Output is correct |
31 |
Correct |
3 ms |
13916 KB |
Output is correct |
32 |
Correct |
2 ms |
13660 KB |
Output is correct |
33 |
Correct |
3 ms |
13656 KB |
Output is correct |
34 |
Correct |
2 ms |
13660 KB |
Output is correct |
35 |
Correct |
2 ms |
13660 KB |
Output is correct |
36 |
Correct |
3 ms |
13816 KB |
Output is correct |
37 |
Correct |
3 ms |
13916 KB |
Output is correct |
38 |
Correct |
3 ms |
13888 KB |
Output is correct |
39 |
Correct |
2 ms |
13912 KB |
Output is correct |
40 |
Correct |
2 ms |
13660 KB |
Output is correct |
41 |
Correct |
2 ms |
13660 KB |
Output is correct |
42 |
Correct |
2 ms |
13752 KB |
Output is correct |
43 |
Correct |
3 ms |
13912 KB |
Output is correct |
44 |
Correct |
2 ms |
13660 KB |
Output is correct |
45 |
Correct |
2 ms |
13660 KB |
Output is correct |
46 |
Correct |
3 ms |
13916 KB |
Output is correct |
47 |
Correct |
3 ms |
13660 KB |
Output is correct |
48 |
Correct |
2 ms |
13660 KB |
Output is correct |
49 |
Correct |
2 ms |
13916 KB |
Output is correct |
50 |
Correct |
2 ms |
13656 KB |
Output is correct |
51 |
Correct |
2 ms |
13656 KB |
Output is correct |
52 |
Correct |
2 ms |
13916 KB |
Output is correct |
53 |
Correct |
2 ms |
13916 KB |
Output is correct |
54 |
Correct |
2 ms |
13660 KB |
Output is correct |
55 |
Correct |
3 ms |
13660 KB |
Output is correct |
56 |
Correct |
2 ms |
13660 KB |
Output is correct |
57 |
Correct |
2 ms |
13916 KB |
Output is correct |
58 |
Correct |
3 ms |
13916 KB |
Output is correct |
59 |
Correct |
154 ms |
35228 KB |
Output is correct |
60 |
Correct |
162 ms |
37316 KB |
Output is correct |
61 |
Correct |
2 ms |
13660 KB |
Output is correct |
62 |
Correct |
2 ms |
13660 KB |
Output is correct |
63 |
Correct |
130 ms |
32920 KB |
Output is correct |
64 |
Correct |
4 ms |
14680 KB |
Output is correct |
65 |
Correct |
9 ms |
17244 KB |
Output is correct |
66 |
Correct |
58 ms |
39700 KB |
Output is correct |
67 |
Correct |
288 ms |
118856 KB |
Output is correct |
68 |
Correct |
317 ms |
91732 KB |
Output is correct |
69 |
Correct |
6 ms |
14728 KB |
Output is correct |
70 |
Correct |
46 ms |
22252 KB |
Output is correct |
71 |
Correct |
160 ms |
40396 KB |
Output is correct |
72 |
Correct |
148 ms |
39488 KB |
Output is correct |
73 |
Correct |
38 ms |
20176 KB |
Output is correct |
74 |
Correct |
211 ms |
36288 KB |
Output is correct |
75 |
Correct |
16 ms |
16860 KB |
Output is correct |
76 |
Correct |
171 ms |
40112 KB |
Output is correct |
77 |
Correct |
144 ms |
40356 KB |
Output is correct |
78 |
Correct |
19 ms |
19264 KB |
Output is correct |
79 |
Correct |
296 ms |
72452 KB |
Output is correct |
80 |
Correct |
4 ms |
14168 KB |
Output is correct |
81 |
Correct |
49 ms |
22192 KB |
Output is correct |
82 |
Correct |
190 ms |
38332 KB |
Output is correct |
83 |
Correct |
218 ms |
36236 KB |
Output is correct |
84 |
Correct |
195 ms |
36292 KB |
Output is correct |
85 |
Correct |
237 ms |
36436 KB |
Output is correct |
86 |
Correct |
217 ms |
37316 KB |
Output is correct |
87 |
Correct |
233 ms |
37316 KB |
Output is correct |