#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
#include <set>
#include <map>
using namespace std;
typedef long long int ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
#define rep(i, a, b) for (ll i = a; i < b; i++)
#define mp(a, b) make_pair(a, b)
#define sz(a) a.size()
#define pb(a) push_back(a)
ll N;
vvll g;
ll root;
vpll edges;
vll dp_dfs(ll cur, ll par) {
vll res;
bool is_leaf = true;
for (vll::iterator itr = g[cur].begin(); itr != g[cur].end(); itr++) {
if (*itr == par) continue;
is_leaf = false;
vll child = dp_dfs(*itr, cur);
for (vll::iterator t = child.begin(); t != child.end(); t++) res.pb(*t);
if (sz(res) >= 3) {
ll a = res.back(); res.pop_back();
ll b = res.front(); res.erase(res.begin());
edges.pb(mp(a, b));
}
}
if (is_leaf) {
res.pb(cur);
}
return res;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> N;
g.resize(N);
rep(i, 0, N - 1) {
ll tmpa, tmpb;
cin >> tmpa >> tmpb;
tmpa--; tmpb--;
g[tmpa].pb(tmpb);
g[tmpb].pb(tmpa);
}
root = 0;
while (sz(g[root]) == 1) root++;
vll res = dp_dfs(root, -1);
if (sz(res) == 1) {
edges.pb(mp(res[0], root));
} else {
edges.pb(mp(res[0], res[1]));
}
cout << sz(edges) << "\n";
for (vpll::iterator itr = edges.begin(); itr != edges.end(); itr++) {
cout << itr->first + 1 << " " << itr->second + 1 << "\n";
}
cout << flush;
return 0;
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
1 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
212 KB |
Output is correct |
7 |
Correct |
1 ms |
212 KB |
Output is correct |
8 |
Correct |
1 ms |
212 KB |
Output is correct |
9 |
Correct |
1 ms |
212 KB |
Output is correct |
10 |
Correct |
1 ms |
316 KB |
Output is correct |
11 |
Correct |
1 ms |
212 KB |
Output is correct |
12 |
Correct |
1 ms |
212 KB |
Output is correct |
13 |
Correct |
1 ms |
212 KB |
Output is correct |
14 |
Correct |
1 ms |
212 KB |
Output is correct |
15 |
Correct |
1 ms |
212 KB |
Output is correct |
16 |
Correct |
1 ms |
316 KB |
Output is correct |
17 |
Correct |
0 ms |
212 KB |
Output is correct |
18 |
Correct |
1 ms |
324 KB |
Output is correct |
19 |
Correct |
0 ms |
212 KB |
Output is correct |
20 |
Correct |
1 ms |
212 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
1 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
212 KB |
Output is correct |
7 |
Correct |
1 ms |
212 KB |
Output is correct |
8 |
Correct |
1 ms |
212 KB |
Output is correct |
9 |
Correct |
1 ms |
212 KB |
Output is correct |
10 |
Correct |
1 ms |
316 KB |
Output is correct |
11 |
Correct |
1 ms |
212 KB |
Output is correct |
12 |
Correct |
1 ms |
212 KB |
Output is correct |
13 |
Correct |
1 ms |
212 KB |
Output is correct |
14 |
Correct |
1 ms |
212 KB |
Output is correct |
15 |
Correct |
1 ms |
212 KB |
Output is correct |
16 |
Correct |
1 ms |
316 KB |
Output is correct |
17 |
Correct |
0 ms |
212 KB |
Output is correct |
18 |
Correct |
1 ms |
324 KB |
Output is correct |
19 |
Correct |
0 ms |
212 KB |
Output is correct |
20 |
Correct |
1 ms |
212 KB |
Output is correct |
21 |
Correct |
1 ms |
212 KB |
Output is correct |
22 |
Correct |
1 ms |
468 KB |
Output is correct |
23 |
Correct |
1 ms |
468 KB |
Output is correct |
24 |
Correct |
2 ms |
468 KB |
Output is correct |
25 |
Correct |
1 ms |
468 KB |
Output is correct |
26 |
Correct |
1 ms |
340 KB |
Output is correct |
27 |
Correct |
1 ms |
460 KB |
Output is correct |
28 |
Correct |
2 ms |
468 KB |
Output is correct |
29 |
Correct |
1 ms |
340 KB |
Output is correct |
30 |
Correct |
1 ms |
320 KB |
Output is correct |
31 |
Correct |
2 ms |
464 KB |
Output is correct |
32 |
Correct |
1 ms |
212 KB |
Output is correct |
33 |
Correct |
1 ms |
320 KB |
Output is correct |
34 |
Correct |
1 ms |
212 KB |
Output is correct |
35 |
Correct |
1 ms |
316 KB |
Output is correct |
36 |
Correct |
1 ms |
212 KB |
Output is correct |
37 |
Correct |
1 ms |
340 KB |
Output is correct |
38 |
Correct |
1 ms |
468 KB |
Output is correct |
39 |
Correct |
1 ms |
212 KB |
Output is correct |
40 |
Correct |
0 ms |
320 KB |
Output is correct |
41 |
Correct |
1 ms |
212 KB |
Output is correct |
42 |
Correct |
1 ms |
340 KB |
Output is correct |
43 |
Correct |
1 ms |
320 KB |
Output is correct |
44 |
Correct |
1 ms |
212 KB |
Output is correct |
45 |
Correct |
1 ms |
340 KB |
Output is correct |
46 |
Correct |
1 ms |
340 KB |
Output is correct |
47 |
Correct |
1 ms |
212 KB |
Output is correct |
48 |
Correct |
1 ms |
340 KB |
Output is correct |
49 |
Correct |
1 ms |
340 KB |
Output is correct |
50 |
Correct |
1 ms |
212 KB |
Output is correct |
51 |
Correct |
1 ms |
212 KB |
Output is correct |
52 |
Correct |
1 ms |
340 KB |
Output is correct |
53 |
Correct |
1 ms |
340 KB |
Output is correct |
54 |
Correct |
1 ms |
212 KB |
Output is correct |
55 |
Correct |
1 ms |
340 KB |
Output is correct |
56 |
Correct |
1 ms |
316 KB |
Output is correct |
57 |
Correct |
1 ms |
340 KB |
Output is correct |
58 |
Correct |
1 ms |
460 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
1 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
212 KB |
Output is correct |
7 |
Correct |
1 ms |
212 KB |
Output is correct |
8 |
Correct |
1 ms |
212 KB |
Output is correct |
9 |
Correct |
1 ms |
212 KB |
Output is correct |
10 |
Correct |
1 ms |
316 KB |
Output is correct |
11 |
Correct |
1 ms |
212 KB |
Output is correct |
12 |
Correct |
1 ms |
212 KB |
Output is correct |
13 |
Correct |
1 ms |
212 KB |
Output is correct |
14 |
Correct |
1 ms |
212 KB |
Output is correct |
15 |
Correct |
1 ms |
212 KB |
Output is correct |
16 |
Correct |
1 ms |
316 KB |
Output is correct |
17 |
Correct |
0 ms |
212 KB |
Output is correct |
18 |
Correct |
1 ms |
324 KB |
Output is correct |
19 |
Correct |
0 ms |
212 KB |
Output is correct |
20 |
Correct |
1 ms |
212 KB |
Output is correct |
21 |
Correct |
1 ms |
212 KB |
Output is correct |
22 |
Correct |
1 ms |
468 KB |
Output is correct |
23 |
Correct |
1 ms |
468 KB |
Output is correct |
24 |
Correct |
2 ms |
468 KB |
Output is correct |
25 |
Correct |
1 ms |
468 KB |
Output is correct |
26 |
Correct |
1 ms |
340 KB |
Output is correct |
27 |
Correct |
1 ms |
460 KB |
Output is correct |
28 |
Correct |
2 ms |
468 KB |
Output is correct |
29 |
Correct |
1 ms |
340 KB |
Output is correct |
30 |
Correct |
1 ms |
320 KB |
Output is correct |
31 |
Correct |
2 ms |
464 KB |
Output is correct |
32 |
Correct |
1 ms |
212 KB |
Output is correct |
33 |
Correct |
1 ms |
320 KB |
Output is correct |
34 |
Correct |
1 ms |
212 KB |
Output is correct |
35 |
Correct |
1 ms |
316 KB |
Output is correct |
36 |
Correct |
1 ms |
212 KB |
Output is correct |
37 |
Correct |
1 ms |
340 KB |
Output is correct |
38 |
Correct |
1 ms |
468 KB |
Output is correct |
39 |
Correct |
1 ms |
212 KB |
Output is correct |
40 |
Correct |
0 ms |
320 KB |
Output is correct |
41 |
Correct |
1 ms |
212 KB |
Output is correct |
42 |
Correct |
1 ms |
340 KB |
Output is correct |
43 |
Correct |
1 ms |
320 KB |
Output is correct |
44 |
Correct |
1 ms |
212 KB |
Output is correct |
45 |
Correct |
1 ms |
340 KB |
Output is correct |
46 |
Correct |
1 ms |
340 KB |
Output is correct |
47 |
Correct |
1 ms |
212 KB |
Output is correct |
48 |
Correct |
1 ms |
340 KB |
Output is correct |
49 |
Correct |
1 ms |
340 KB |
Output is correct |
50 |
Correct |
1 ms |
212 KB |
Output is correct |
51 |
Correct |
1 ms |
212 KB |
Output is correct |
52 |
Correct |
1 ms |
340 KB |
Output is correct |
53 |
Correct |
1 ms |
340 KB |
Output is correct |
54 |
Correct |
1 ms |
212 KB |
Output is correct |
55 |
Correct |
1 ms |
340 KB |
Output is correct |
56 |
Correct |
1 ms |
316 KB |
Output is correct |
57 |
Correct |
1 ms |
340 KB |
Output is correct |
58 |
Correct |
1 ms |
460 KB |
Output is correct |
59 |
Correct |
368 ms |
39344 KB |
Output is correct |
60 |
Correct |
441 ms |
43360 KB |
Output is correct |
61 |
Correct |
0 ms |
212 KB |
Output is correct |
62 |
Correct |
1 ms |
320 KB |
Output is correct |
63 |
Correct |
318 ms |
34372 KB |
Output is correct |
64 |
Correct |
3 ms |
1236 KB |
Output is correct |
65 |
Correct |
12 ms |
4208 KB |
Output is correct |
66 |
Correct |
151 ms |
33600 KB |
Output is correct |
67 |
Correct |
493 ms |
67860 KB |
Output is correct |
68 |
Correct |
494 ms |
70252 KB |
Output is correct |
69 |
Correct |
6 ms |
1628 KB |
Output is correct |
70 |
Correct |
100 ms |
15268 KB |
Output is correct |
71 |
Correct |
319 ms |
45816 KB |
Output is correct |
72 |
Correct |
363 ms |
44204 KB |
Output is correct |
73 |
Correct |
79 ms |
11584 KB |
Output is correct |
74 |
Correct |
457 ms |
41076 KB |
Output is correct |
75 |
Correct |
23 ms |
5172 KB |
Output is correct |
76 |
Correct |
289 ms |
45344 KB |
Output is correct |
77 |
Correct |
309 ms |
45552 KB |
Output is correct |
78 |
Correct |
26 ms |
7032 KB |
Output is correct |
79 |
Correct |
521 ms |
63256 KB |
Output is correct |
80 |
Correct |
2 ms |
596 KB |
Output is correct |
81 |
Correct |
120 ms |
14820 KB |
Output is correct |
82 |
Correct |
388 ms |
43268 KB |
Output is correct |
83 |
Correct |
486 ms |
41156 KB |
Output is correct |
84 |
Correct |
451 ms |
41188 KB |
Output is correct |
85 |
Correct |
477 ms |
41140 KB |
Output is correct |
86 |
Correct |
456 ms |
43412 KB |
Output is correct |
87 |
Correct |
486 ms |
43424 KB |
Output is correct |