#include <bits/stdc++.h>
using namespace std;
const int MAXN = 5e5 + 10;
int v[MAXN], cnt;
vector<int> grafo[MAXN];
int read()
{
int x=0,f=1;char c=getchar();
while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
while (c>='0'&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar();
return x*f;
}
void dfs(int u, int p)
{
for (int i=0; i<grafo[u].size(); i++){
int v = grafo[u][i];
if (v == p) continue;
dfs(v, u);
}
if (grafo[u].size() == 1) v[++cnt] = u;
}
int main(){
int n=read();
for(int i=1; i<n; i++){
int a, b;
a=read();
b=read();
grafo[a].push_back(b);
grafo[b].push_back(a);
}
for(int i=1; i<=n; i++){
if(grafo[i].size()>1){
dfs(i, 0);
break;
}
}
int ans = (cnt+1)/2;
cout << ans << "\n";
for(int i=1; i<ans; i++){
cout << v[i] << " " << v[i+ans] << "\n";
}
if(cnt&1){
cout << v[ans] << " " << v[1] << "\n";
}
else{
cout << v[ans] << " " << v[cnt] << "\n";
}
return 0;
}
Compilation message
net.cpp: In function 'void dfs(int, int)':
net.cpp:21:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i=0; i<grafo[u].size(); i++){
~^~~~~~~~~~~~~~~~
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
12 ms |
12032 KB |
Output is correct |
2 |
Correct |
12 ms |
12032 KB |
Output is correct |
3 |
Correct |
12 ms |
12032 KB |
Output is correct |
4 |
Correct |
11 ms |
12032 KB |
Output is correct |
5 |
Correct |
12 ms |
12160 KB |
Output is correct |
6 |
Correct |
12 ms |
12032 KB |
Output is correct |
7 |
Correct |
11 ms |
12032 KB |
Output is correct |
8 |
Correct |
14 ms |
12032 KB |
Output is correct |
9 |
Correct |
11 ms |
12032 KB |
Output is correct |
10 |
Correct |
13 ms |
12160 KB |
Output is correct |
11 |
Correct |
12 ms |
12160 KB |
Output is correct |
12 |
Correct |
11 ms |
12032 KB |
Output is correct |
13 |
Correct |
11 ms |
12032 KB |
Output is correct |
14 |
Correct |
12 ms |
12032 KB |
Output is correct |
15 |
Correct |
13 ms |
12004 KB |
Output is correct |
16 |
Correct |
14 ms |
12032 KB |
Output is correct |
17 |
Correct |
16 ms |
12160 KB |
Output is correct |
18 |
Correct |
14 ms |
12080 KB |
Output is correct |
19 |
Correct |
13 ms |
12032 KB |
Output is correct |
20 |
Correct |
13 ms |
12032 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
12 ms |
12032 KB |
Output is correct |
2 |
Correct |
12 ms |
12032 KB |
Output is correct |
3 |
Correct |
12 ms |
12032 KB |
Output is correct |
4 |
Correct |
11 ms |
12032 KB |
Output is correct |
5 |
Correct |
12 ms |
12160 KB |
Output is correct |
6 |
Correct |
12 ms |
12032 KB |
Output is correct |
7 |
Correct |
11 ms |
12032 KB |
Output is correct |
8 |
Correct |
14 ms |
12032 KB |
Output is correct |
9 |
Correct |
11 ms |
12032 KB |
Output is correct |
10 |
Correct |
13 ms |
12160 KB |
Output is correct |
11 |
Correct |
12 ms |
12160 KB |
Output is correct |
12 |
Correct |
11 ms |
12032 KB |
Output is correct |
13 |
Correct |
11 ms |
12032 KB |
Output is correct |
14 |
Correct |
12 ms |
12032 KB |
Output is correct |
15 |
Correct |
13 ms |
12004 KB |
Output is correct |
16 |
Correct |
14 ms |
12032 KB |
Output is correct |
17 |
Correct |
16 ms |
12160 KB |
Output is correct |
18 |
Correct |
14 ms |
12080 KB |
Output is correct |
19 |
Correct |
13 ms |
12032 KB |
Output is correct |
20 |
Correct |
13 ms |
12032 KB |
Output is correct |
21 |
Correct |
11 ms |
12032 KB |
Output is correct |
22 |
Correct |
13 ms |
12160 KB |
Output is correct |
23 |
Correct |
12 ms |
12160 KB |
Output is correct |
24 |
Correct |
14 ms |
12288 KB |
Output is correct |
25 |
Correct |
11 ms |
12160 KB |
Output is correct |
26 |
Correct |
15 ms |
12160 KB |
Output is correct |
27 |
Correct |
12 ms |
12160 KB |
Output is correct |
28 |
Correct |
12 ms |
12160 KB |
Output is correct |
29 |
Correct |
12 ms |
12160 KB |
Output is correct |
30 |
Correct |
11 ms |
12032 KB |
Output is correct |
31 |
Correct |
13 ms |
12160 KB |
Output is correct |
32 |
Correct |
12 ms |
12032 KB |
Output is correct |
33 |
Correct |
16 ms |
12032 KB |
Output is correct |
34 |
Correct |
14 ms |
12032 KB |
Output is correct |
35 |
Correct |
12 ms |
12032 KB |
Output is correct |
36 |
Correct |
13 ms |
12160 KB |
Output is correct |
37 |
Correct |
12 ms |
12160 KB |
Output is correct |
38 |
Correct |
11 ms |
12160 KB |
Output is correct |
39 |
Correct |
11 ms |
12032 KB |
Output is correct |
40 |
Correct |
12 ms |
12032 KB |
Output is correct |
41 |
Correct |
11 ms |
12032 KB |
Output is correct |
42 |
Correct |
12 ms |
12160 KB |
Output is correct |
43 |
Correct |
12 ms |
12160 KB |
Output is correct |
44 |
Correct |
13 ms |
12032 KB |
Output is correct |
45 |
Correct |
12 ms |
12032 KB |
Output is correct |
46 |
Correct |
14 ms |
12032 KB |
Output is correct |
47 |
Correct |
12 ms |
12032 KB |
Output is correct |
48 |
Correct |
12 ms |
12032 KB |
Output is correct |
49 |
Correct |
14 ms |
12160 KB |
Output is correct |
50 |
Correct |
11 ms |
12032 KB |
Output is correct |
51 |
Correct |
12 ms |
12032 KB |
Output is correct |
52 |
Correct |
12 ms |
12032 KB |
Output is correct |
53 |
Correct |
13 ms |
12160 KB |
Output is correct |
54 |
Correct |
16 ms |
12024 KB |
Output is correct |
55 |
Correct |
12 ms |
12160 KB |
Output is correct |
56 |
Correct |
11 ms |
12032 KB |
Output is correct |
57 |
Correct |
12 ms |
12160 KB |
Output is correct |
58 |
Correct |
14 ms |
12160 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
12 ms |
12032 KB |
Output is correct |
2 |
Correct |
12 ms |
12032 KB |
Output is correct |
3 |
Correct |
12 ms |
12032 KB |
Output is correct |
4 |
Correct |
11 ms |
12032 KB |
Output is correct |
5 |
Correct |
12 ms |
12160 KB |
Output is correct |
6 |
Correct |
12 ms |
12032 KB |
Output is correct |
7 |
Correct |
11 ms |
12032 KB |
Output is correct |
8 |
Correct |
14 ms |
12032 KB |
Output is correct |
9 |
Correct |
11 ms |
12032 KB |
Output is correct |
10 |
Correct |
13 ms |
12160 KB |
Output is correct |
11 |
Correct |
12 ms |
12160 KB |
Output is correct |
12 |
Correct |
11 ms |
12032 KB |
Output is correct |
13 |
Correct |
11 ms |
12032 KB |
Output is correct |
14 |
Correct |
12 ms |
12032 KB |
Output is correct |
15 |
Correct |
13 ms |
12004 KB |
Output is correct |
16 |
Correct |
14 ms |
12032 KB |
Output is correct |
17 |
Correct |
16 ms |
12160 KB |
Output is correct |
18 |
Correct |
14 ms |
12080 KB |
Output is correct |
19 |
Correct |
13 ms |
12032 KB |
Output is correct |
20 |
Correct |
13 ms |
12032 KB |
Output is correct |
21 |
Correct |
11 ms |
12032 KB |
Output is correct |
22 |
Correct |
13 ms |
12160 KB |
Output is correct |
23 |
Correct |
12 ms |
12160 KB |
Output is correct |
24 |
Correct |
14 ms |
12288 KB |
Output is correct |
25 |
Correct |
11 ms |
12160 KB |
Output is correct |
26 |
Correct |
15 ms |
12160 KB |
Output is correct |
27 |
Correct |
12 ms |
12160 KB |
Output is correct |
28 |
Correct |
12 ms |
12160 KB |
Output is correct |
29 |
Correct |
12 ms |
12160 KB |
Output is correct |
30 |
Correct |
11 ms |
12032 KB |
Output is correct |
31 |
Correct |
13 ms |
12160 KB |
Output is correct |
32 |
Correct |
12 ms |
12032 KB |
Output is correct |
33 |
Correct |
16 ms |
12032 KB |
Output is correct |
34 |
Correct |
14 ms |
12032 KB |
Output is correct |
35 |
Correct |
12 ms |
12032 KB |
Output is correct |
36 |
Correct |
13 ms |
12160 KB |
Output is correct |
37 |
Correct |
12 ms |
12160 KB |
Output is correct |
38 |
Correct |
11 ms |
12160 KB |
Output is correct |
39 |
Correct |
11 ms |
12032 KB |
Output is correct |
40 |
Correct |
12 ms |
12032 KB |
Output is correct |
41 |
Correct |
11 ms |
12032 KB |
Output is correct |
42 |
Correct |
12 ms |
12160 KB |
Output is correct |
43 |
Correct |
12 ms |
12160 KB |
Output is correct |
44 |
Correct |
13 ms |
12032 KB |
Output is correct |
45 |
Correct |
12 ms |
12032 KB |
Output is correct |
46 |
Correct |
14 ms |
12032 KB |
Output is correct |
47 |
Correct |
12 ms |
12032 KB |
Output is correct |
48 |
Correct |
12 ms |
12032 KB |
Output is correct |
49 |
Correct |
14 ms |
12160 KB |
Output is correct |
50 |
Correct |
11 ms |
12032 KB |
Output is correct |
51 |
Correct |
12 ms |
12032 KB |
Output is correct |
52 |
Correct |
12 ms |
12032 KB |
Output is correct |
53 |
Correct |
13 ms |
12160 KB |
Output is correct |
54 |
Correct |
16 ms |
12024 KB |
Output is correct |
55 |
Correct |
12 ms |
12160 KB |
Output is correct |
56 |
Correct |
11 ms |
12032 KB |
Output is correct |
57 |
Correct |
12 ms |
12160 KB |
Output is correct |
58 |
Correct |
14 ms |
12160 KB |
Output is correct |
59 |
Correct |
458 ms |
29972 KB |
Output is correct |
60 |
Correct |
513 ms |
32120 KB |
Output is correct |
61 |
Correct |
12 ms |
12032 KB |
Output is correct |
62 |
Correct |
20 ms |
12032 KB |
Output is correct |
63 |
Correct |
387 ms |
28144 KB |
Output is correct |
64 |
Correct |
16 ms |
12412 KB |
Output is correct |
65 |
Correct |
23 ms |
13696 KB |
Output is correct |
66 |
Correct |
194 ms |
25720 KB |
Output is correct |
67 |
Correct |
599 ms |
40440 KB |
Output is correct |
68 |
Correct |
559 ms |
40976 KB |
Output is correct |
69 |
Correct |
18 ms |
12672 KB |
Output is correct |
70 |
Correct |
107 ms |
19092 KB |
Output is correct |
71 |
Correct |
358 ms |
35044 KB |
Output is correct |
72 |
Correct |
351 ms |
34180 KB |
Output is correct |
73 |
Correct |
142 ms |
17444 KB |
Output is correct |
74 |
Correct |
621 ms |
30968 KB |
Output is correct |
75 |
Correct |
51 ms |
14584 KB |
Output is correct |
76 |
Correct |
483 ms |
34872 KB |
Output is correct |
77 |
Correct |
311 ms |
34904 KB |
Output is correct |
78 |
Correct |
38 ms |
14924 KB |
Output is correct |
79 |
Correct |
601 ms |
38580 KB |
Output is correct |
80 |
Correct |
13 ms |
12288 KB |
Output is correct |
81 |
Correct |
125 ms |
19096 KB |
Output is correct |
82 |
Correct |
449 ms |
33068 KB |
Output is correct |
83 |
Correct |
544 ms |
30940 KB |
Output is correct |
84 |
Correct |
596 ms |
31000 KB |
Output is correct |
85 |
Correct |
675 ms |
30924 KB |
Output is correct |
86 |
Correct |
536 ms |
31996 KB |
Output is correct |
87 |
Correct |
546 ms |
31964 KB |
Output is correct |