#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define F first
#define S second
using namespace std;
const int N = 5e5+5;
vector<int> adj[N], lo[N], ch[N];
vector<pii> edge;
void dfs1(int v, int p) {
for (int u : adj[v])
if (u != p) {
ch[v].push_back(u);
dfs1(u, v);
}
}
void dfs2(int v) {
if (ch[v].size() == 0) {
lo[v].push_back(v);
return;
}
vector<int> a, b;
for (int u : ch[v]) {
dfs2(u);
if (lo[u].size() == 2) {
a.push_back(lo[u][0]);
a.push_back(lo[u][1]);
}
else
b.push_back(lo[u][0]);
}
for (int x : b)
a.push_back(x);
lo[v].push_back(a[0]);
for (int i = 1; i < a.size()-1; i += 2)
edge.push_back({a[i], a[i+1]});
if (!(a.size() & 1))
lo[v].push_back(a.back());
}
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int n, r;
cin >> n;
for (int i = 0; i < n-1; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for (r = 1; r <= n; r++)
if (adj[r].size() == 1)
break;
dfs1(r, r);
dfs2(r);
for (int x : lo[r])
edge.push_back({r, x});
cout << edge.size() << endl;
for (pii x : edge)
cout << x.F << ' ' << x.S << endl;
}
Compilation message
net.cpp: In function 'void dfs2(int)':
net.cpp:41:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
41 | for (int i = 1; i < a.size()-1; i += 2)
| ~~^~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
18 ms |
35540 KB |
Output is correct |
2 |
Correct |
18 ms |
35540 KB |
Output is correct |
3 |
Correct |
18 ms |
35416 KB |
Output is correct |
4 |
Correct |
18 ms |
35540 KB |
Output is correct |
5 |
Correct |
19 ms |
35540 KB |
Output is correct |
6 |
Correct |
18 ms |
35540 KB |
Output is correct |
7 |
Correct |
21 ms |
35540 KB |
Output is correct |
8 |
Correct |
18 ms |
35512 KB |
Output is correct |
9 |
Correct |
18 ms |
35432 KB |
Output is correct |
10 |
Correct |
19 ms |
35548 KB |
Output is correct |
11 |
Correct |
19 ms |
35540 KB |
Output is correct |
12 |
Correct |
18 ms |
35436 KB |
Output is correct |
13 |
Correct |
18 ms |
35520 KB |
Output is correct |
14 |
Correct |
20 ms |
35456 KB |
Output is correct |
15 |
Correct |
18 ms |
35540 KB |
Output is correct |
16 |
Correct |
18 ms |
35544 KB |
Output is correct |
17 |
Correct |
18 ms |
35460 KB |
Output is correct |
18 |
Correct |
19 ms |
35444 KB |
Output is correct |
19 |
Correct |
19 ms |
35540 KB |
Output is correct |
20 |
Correct |
18 ms |
35540 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
18 ms |
35540 KB |
Output is correct |
2 |
Correct |
18 ms |
35540 KB |
Output is correct |
3 |
Correct |
18 ms |
35416 KB |
Output is correct |
4 |
Correct |
18 ms |
35540 KB |
Output is correct |
5 |
Correct |
19 ms |
35540 KB |
Output is correct |
6 |
Correct |
18 ms |
35540 KB |
Output is correct |
7 |
Correct |
21 ms |
35540 KB |
Output is correct |
8 |
Correct |
18 ms |
35512 KB |
Output is correct |
9 |
Correct |
18 ms |
35432 KB |
Output is correct |
10 |
Correct |
19 ms |
35548 KB |
Output is correct |
11 |
Correct |
19 ms |
35540 KB |
Output is correct |
12 |
Correct |
18 ms |
35436 KB |
Output is correct |
13 |
Correct |
18 ms |
35520 KB |
Output is correct |
14 |
Correct |
20 ms |
35456 KB |
Output is correct |
15 |
Correct |
18 ms |
35540 KB |
Output is correct |
16 |
Correct |
18 ms |
35544 KB |
Output is correct |
17 |
Correct |
18 ms |
35460 KB |
Output is correct |
18 |
Correct |
19 ms |
35444 KB |
Output is correct |
19 |
Correct |
19 ms |
35540 KB |
Output is correct |
20 |
Correct |
18 ms |
35540 KB |
Output is correct |
21 |
Correct |
17 ms |
35468 KB |
Output is correct |
22 |
Correct |
20 ms |
35676 KB |
Output is correct |
23 |
Correct |
19 ms |
35660 KB |
Output is correct |
24 |
Correct |
22 ms |
35604 KB |
Output is correct |
25 |
Correct |
20 ms |
35696 KB |
Output is correct |
26 |
Correct |
19 ms |
35608 KB |
Output is correct |
27 |
Correct |
21 ms |
35660 KB |
Output is correct |
28 |
Correct |
20 ms |
35724 KB |
Output is correct |
29 |
Correct |
24 ms |
35660 KB |
Output is correct |
30 |
Correct |
18 ms |
35540 KB |
Output is correct |
31 |
Correct |
23 ms |
35716 KB |
Output is correct |
32 |
Correct |
18 ms |
35548 KB |
Output is correct |
33 |
Correct |
18 ms |
35540 KB |
Output is correct |
34 |
Correct |
17 ms |
35540 KB |
Output is correct |
35 |
Correct |
20 ms |
35464 KB |
Output is correct |
36 |
Correct |
18 ms |
35540 KB |
Output is correct |
37 |
Correct |
18 ms |
35552 KB |
Output is correct |
38 |
Correct |
19 ms |
35668 KB |
Output is correct |
39 |
Correct |
22 ms |
35540 KB |
Output is correct |
40 |
Correct |
18 ms |
35520 KB |
Output is correct |
41 |
Correct |
20 ms |
35524 KB |
Output is correct |
42 |
Correct |
19 ms |
35540 KB |
Output is correct |
43 |
Correct |
18 ms |
35540 KB |
Output is correct |
44 |
Correct |
19 ms |
35540 KB |
Output is correct |
45 |
Correct |
18 ms |
35548 KB |
Output is correct |
46 |
Correct |
19 ms |
35540 KB |
Output is correct |
47 |
Correct |
17 ms |
35540 KB |
Output is correct |
48 |
Correct |
18 ms |
35472 KB |
Output is correct |
49 |
Correct |
20 ms |
35600 KB |
Output is correct |
50 |
Correct |
17 ms |
35552 KB |
Output is correct |
51 |
Correct |
19 ms |
35464 KB |
Output is correct |
52 |
Correct |
18 ms |
35580 KB |
Output is correct |
53 |
Correct |
19 ms |
35680 KB |
Output is correct |
54 |
Correct |
17 ms |
35544 KB |
Output is correct |
55 |
Correct |
17 ms |
35540 KB |
Output is correct |
56 |
Correct |
18 ms |
35548 KB |
Output is correct |
57 |
Correct |
19 ms |
35716 KB |
Output is correct |
58 |
Correct |
21 ms |
35608 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
18 ms |
35540 KB |
Output is correct |
2 |
Correct |
18 ms |
35540 KB |
Output is correct |
3 |
Correct |
18 ms |
35416 KB |
Output is correct |
4 |
Correct |
18 ms |
35540 KB |
Output is correct |
5 |
Correct |
19 ms |
35540 KB |
Output is correct |
6 |
Correct |
18 ms |
35540 KB |
Output is correct |
7 |
Correct |
21 ms |
35540 KB |
Output is correct |
8 |
Correct |
18 ms |
35512 KB |
Output is correct |
9 |
Correct |
18 ms |
35432 KB |
Output is correct |
10 |
Correct |
19 ms |
35548 KB |
Output is correct |
11 |
Correct |
19 ms |
35540 KB |
Output is correct |
12 |
Correct |
18 ms |
35436 KB |
Output is correct |
13 |
Correct |
18 ms |
35520 KB |
Output is correct |
14 |
Correct |
20 ms |
35456 KB |
Output is correct |
15 |
Correct |
18 ms |
35540 KB |
Output is correct |
16 |
Correct |
18 ms |
35544 KB |
Output is correct |
17 |
Correct |
18 ms |
35460 KB |
Output is correct |
18 |
Correct |
19 ms |
35444 KB |
Output is correct |
19 |
Correct |
19 ms |
35540 KB |
Output is correct |
20 |
Correct |
18 ms |
35540 KB |
Output is correct |
21 |
Correct |
17 ms |
35468 KB |
Output is correct |
22 |
Correct |
20 ms |
35676 KB |
Output is correct |
23 |
Correct |
19 ms |
35660 KB |
Output is correct |
24 |
Correct |
22 ms |
35604 KB |
Output is correct |
25 |
Correct |
20 ms |
35696 KB |
Output is correct |
26 |
Correct |
19 ms |
35608 KB |
Output is correct |
27 |
Correct |
21 ms |
35660 KB |
Output is correct |
28 |
Correct |
20 ms |
35724 KB |
Output is correct |
29 |
Correct |
24 ms |
35660 KB |
Output is correct |
30 |
Correct |
18 ms |
35540 KB |
Output is correct |
31 |
Correct |
23 ms |
35716 KB |
Output is correct |
32 |
Correct |
18 ms |
35548 KB |
Output is correct |
33 |
Correct |
18 ms |
35540 KB |
Output is correct |
34 |
Correct |
17 ms |
35540 KB |
Output is correct |
35 |
Correct |
20 ms |
35464 KB |
Output is correct |
36 |
Correct |
18 ms |
35540 KB |
Output is correct |
37 |
Correct |
18 ms |
35552 KB |
Output is correct |
38 |
Correct |
19 ms |
35668 KB |
Output is correct |
39 |
Correct |
22 ms |
35540 KB |
Output is correct |
40 |
Correct |
18 ms |
35520 KB |
Output is correct |
41 |
Correct |
20 ms |
35524 KB |
Output is correct |
42 |
Correct |
19 ms |
35540 KB |
Output is correct |
43 |
Correct |
18 ms |
35540 KB |
Output is correct |
44 |
Correct |
19 ms |
35540 KB |
Output is correct |
45 |
Correct |
18 ms |
35548 KB |
Output is correct |
46 |
Correct |
19 ms |
35540 KB |
Output is correct |
47 |
Correct |
17 ms |
35540 KB |
Output is correct |
48 |
Correct |
18 ms |
35472 KB |
Output is correct |
49 |
Correct |
20 ms |
35600 KB |
Output is correct |
50 |
Correct |
17 ms |
35552 KB |
Output is correct |
51 |
Correct |
19 ms |
35464 KB |
Output is correct |
52 |
Correct |
18 ms |
35580 KB |
Output is correct |
53 |
Correct |
19 ms |
35680 KB |
Output is correct |
54 |
Correct |
17 ms |
35544 KB |
Output is correct |
55 |
Correct |
17 ms |
35540 KB |
Output is correct |
56 |
Correct |
18 ms |
35548 KB |
Output is correct |
57 |
Correct |
19 ms |
35716 KB |
Output is correct |
58 |
Correct |
21 ms |
35608 KB |
Output is correct |
59 |
Correct |
649 ms |
74300 KB |
Output is correct |
60 |
Correct |
768 ms |
77104 KB |
Output is correct |
61 |
Correct |
18 ms |
35540 KB |
Output is correct |
62 |
Correct |
18 ms |
35540 KB |
Output is correct |
63 |
Correct |
592 ms |
69092 KB |
Output is correct |
64 |
Correct |
23 ms |
36424 KB |
Output is correct |
65 |
Correct |
32 ms |
41240 KB |
Output is correct |
66 |
Correct |
194 ms |
77544 KB |
Output is correct |
67 |
Correct |
744 ms |
160724 KB |
Output is correct |
68 |
Correct |
709 ms |
126724 KB |
Output is correct |
69 |
Correct |
40 ms |
36948 KB |
Output is correct |
70 |
Correct |
200 ms |
50116 KB |
Output is correct |
71 |
Correct |
687 ms |
77756 KB |
Output is correct |
72 |
Correct |
683 ms |
78456 KB |
Output is correct |
73 |
Correct |
171 ms |
47420 KB |
Output is correct |
74 |
Correct |
778 ms |
78140 KB |
Output is correct |
75 |
Correct |
74 ms |
40168 KB |
Output is correct |
76 |
Correct |
709 ms |
76424 KB |
Output is correct |
77 |
Correct |
661 ms |
76212 KB |
Output is correct |
78 |
Correct |
66 ms |
42936 KB |
Output is correct |
79 |
Correct |
658 ms |
134720 KB |
Output is correct |
80 |
Correct |
24 ms |
35924 KB |
Output is correct |
81 |
Correct |
201 ms |
49624 KB |
Output is correct |
82 |
Correct |
780 ms |
77792 KB |
Output is correct |
83 |
Correct |
742 ms |
78064 KB |
Output is correct |
84 |
Correct |
766 ms |
78164 KB |
Output is correct |
85 |
Correct |
759 ms |
78140 KB |
Output is correct |
86 |
Correct |
762 ms |
76736 KB |
Output is correct |
87 |
Correct |
789 ms |
76724 KB |
Output is correct |