#include <bits/stdc++.h>
using namespace std;
typedef int64_t llo;
#define mp make_pair
#define pb push_back
#define a first
#define b second
int n;
vector<int> adj[500001];
int co=0;
vector<int> kk;
void dfs(int no,int par=-1){
vector<pair<int,int>> ss[2];
for(auto j:adj[no]){
if(j!=par){
dfs(j,no);
/*cout<<j<<','<<x[0]<<","<<x[1]<<endl;
if(x.size()==1){
ss[0].pb({x[0],-1});
}
else{
ss[1].pb({x[0],x[1]});
}*/
}
}
if(adj[no].size()==1){
co+=1;
kk.pb(no);
}
/* if(no==3){
cout<<','<<ss[1].size()<<","<<ss[0].size()<<endl;
}
if(ss[1].size()%2==0){
for(int i=0;i<(int)(ss[1].size());i+=2){
ans.pb({ss[1][i].a,ss[1][i+1].a});
ans.pb({ss[1][i].b,ss[1][i+1].b});
}
if(ss[0].size()==0){
pair<int,int> x=ans.back();
ans.pop_back();
return {x.a,x.b};
}
for(int i=0;i<(int)(ss[0].size())-1;i+=2){
ans.pb({ss[0][i].a,ss[0][i+1].a});
}
if(ss[0].size()%2==0){
ans.pop_back();
return {ss[0].back().a,ss[0][ss[0].size()-2].a};
}
else{
return {ss[0].back().a};
}
}
else{
for(int i=0;i<(int)(ss[1].size())-1;i+=2){
ans.pb({ss[1][i].a,ss[1][i+1].a});
ans.pb({ss[1][i].b,ss[1][i+1].b});
}
for(int i=0;i<(int)(ss[0].size())-1;i+=2){
ans.pb({ss[0][i].a,ss[0][i+1].a});
}
if(ss[0].size()%2==0){
return {ss[1].back().a,ss[1].back().b};
}
else{
ans.pb({ss[1].back().a,ss[0].back().a});
return {ss[1].back().b};
}
}
*/
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin>>n;
for(int i=0;i<n-1;i++){
int aa,bb;
cin>>aa>>bb;
adj[aa-1].pb(bb-1);
adj[bb-1].pb(aa-1);
}
int r=0;
for(int i=0;i<n;i++){
if(adj[i].size()>1){
r=i;
}
}
dfs(r);
cout<<(co+1)/2<<endl;
for(int i=0;i<(co+1)/2;i++){
// cout<<i<<endl;
cout<<kk[i]+1<<" "<<kk[i+co/2]+1<<endl;
}
/* for(int i=0;i<kk.size()/2;i++){
cout<<kk[i]+1<<" "<<kk[kk.size()-i-1]+1<<endl;
}
if(kk.size()%2==1){
cout<<kk[kk.size()/2]+1<<" "<<r+1<<endl;
}*/
return 0;
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
11 ms |
12032 KB |
Output is correct |
2 |
Correct |
14 ms |
12160 KB |
Output is correct |
3 |
Correct |
13 ms |
12032 KB |
Output is correct |
4 |
Correct |
11 ms |
12032 KB |
Output is correct |
5 |
Correct |
11 ms |
12160 KB |
Output is correct |
6 |
Correct |
14 ms |
12032 KB |
Output is correct |
7 |
Correct |
11 ms |
12032 KB |
Output is correct |
8 |
Correct |
11 ms |
12160 KB |
Output is correct |
9 |
Correct |
11 ms |
12032 KB |
Output is correct |
10 |
Correct |
11 ms |
12032 KB |
Output is correct |
11 |
Correct |
13 ms |
12032 KB |
Output is correct |
12 |
Correct |
11 ms |
12160 KB |
Output is correct |
13 |
Correct |
11 ms |
11904 KB |
Output is correct |
14 |
Correct |
11 ms |
12160 KB |
Output is correct |
15 |
Correct |
11 ms |
12160 KB |
Output is correct |
16 |
Correct |
13 ms |
12032 KB |
Output is correct |
17 |
Correct |
11 ms |
12160 KB |
Output is correct |
18 |
Correct |
11 ms |
12032 KB |
Output is correct |
19 |
Correct |
11 ms |
12032 KB |
Output is correct |
20 |
Correct |
11 ms |
12032 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
11 ms |
12032 KB |
Output is correct |
2 |
Correct |
14 ms |
12160 KB |
Output is correct |
3 |
Correct |
13 ms |
12032 KB |
Output is correct |
4 |
Correct |
11 ms |
12032 KB |
Output is correct |
5 |
Correct |
11 ms |
12160 KB |
Output is correct |
6 |
Correct |
14 ms |
12032 KB |
Output is correct |
7 |
Correct |
11 ms |
12032 KB |
Output is correct |
8 |
Correct |
11 ms |
12160 KB |
Output is correct |
9 |
Correct |
11 ms |
12032 KB |
Output is correct |
10 |
Correct |
11 ms |
12032 KB |
Output is correct |
11 |
Correct |
13 ms |
12032 KB |
Output is correct |
12 |
Correct |
11 ms |
12160 KB |
Output is correct |
13 |
Correct |
11 ms |
11904 KB |
Output is correct |
14 |
Correct |
11 ms |
12160 KB |
Output is correct |
15 |
Correct |
11 ms |
12160 KB |
Output is correct |
16 |
Correct |
13 ms |
12032 KB |
Output is correct |
17 |
Correct |
11 ms |
12160 KB |
Output is correct |
18 |
Correct |
11 ms |
12032 KB |
Output is correct |
19 |
Correct |
11 ms |
12032 KB |
Output is correct |
20 |
Correct |
11 ms |
12032 KB |
Output is correct |
21 |
Correct |
11 ms |
12032 KB |
Output is correct |
22 |
Correct |
15 ms |
12288 KB |
Output is correct |
23 |
Correct |
15 ms |
12288 KB |
Output is correct |
24 |
Correct |
14 ms |
12160 KB |
Output is correct |
25 |
Correct |
15 ms |
12160 KB |
Output is correct |
26 |
Correct |
13 ms |
12160 KB |
Output is correct |
27 |
Correct |
14 ms |
12160 KB |
Output is correct |
28 |
Correct |
16 ms |
12160 KB |
Output is correct |
29 |
Correct |
13 ms |
12160 KB |
Output is correct |
30 |
Correct |
13 ms |
12160 KB |
Output is correct |
31 |
Correct |
14 ms |
12288 KB |
Output is correct |
32 |
Correct |
13 ms |
12032 KB |
Output is correct |
33 |
Correct |
13 ms |
12032 KB |
Output is correct |
34 |
Correct |
11 ms |
12160 KB |
Output is correct |
35 |
Correct |
11 ms |
12032 KB |
Output is correct |
36 |
Correct |
12 ms |
12160 KB |
Output is correct |
37 |
Correct |
12 ms |
12160 KB |
Output is correct |
38 |
Correct |
12 ms |
12160 KB |
Output is correct |
39 |
Correct |
11 ms |
12032 KB |
Output is correct |
40 |
Correct |
14 ms |
12032 KB |
Output is correct |
41 |
Correct |
11 ms |
12032 KB |
Output is correct |
42 |
Correct |
12 ms |
12032 KB |
Output is correct |
43 |
Correct |
13 ms |
12160 KB |
Output is correct |
44 |
Correct |
12 ms |
12032 KB |
Output is correct |
45 |
Correct |
14 ms |
12032 KB |
Output is correct |
46 |
Correct |
12 ms |
12160 KB |
Output is correct |
47 |
Correct |
12 ms |
12032 KB |
Output is correct |
48 |
Correct |
14 ms |
12160 KB |
Output is correct |
49 |
Correct |
13 ms |
12160 KB |
Output is correct |
50 |
Correct |
12 ms |
12032 KB |
Output is correct |
51 |
Correct |
13 ms |
12032 KB |
Output is correct |
52 |
Correct |
12 ms |
12032 KB |
Output is correct |
53 |
Correct |
12 ms |
12160 KB |
Output is correct |
54 |
Correct |
13 ms |
12160 KB |
Output is correct |
55 |
Correct |
14 ms |
12160 KB |
Output is correct |
56 |
Correct |
12 ms |
12032 KB |
Output is correct |
57 |
Correct |
12 ms |
12160 KB |
Output is correct |
58 |
Correct |
14 ms |
12288 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
11 ms |
12032 KB |
Output is correct |
2 |
Correct |
14 ms |
12160 KB |
Output is correct |
3 |
Correct |
13 ms |
12032 KB |
Output is correct |
4 |
Correct |
11 ms |
12032 KB |
Output is correct |
5 |
Correct |
11 ms |
12160 KB |
Output is correct |
6 |
Correct |
14 ms |
12032 KB |
Output is correct |
7 |
Correct |
11 ms |
12032 KB |
Output is correct |
8 |
Correct |
11 ms |
12160 KB |
Output is correct |
9 |
Correct |
11 ms |
12032 KB |
Output is correct |
10 |
Correct |
11 ms |
12032 KB |
Output is correct |
11 |
Correct |
13 ms |
12032 KB |
Output is correct |
12 |
Correct |
11 ms |
12160 KB |
Output is correct |
13 |
Correct |
11 ms |
11904 KB |
Output is correct |
14 |
Correct |
11 ms |
12160 KB |
Output is correct |
15 |
Correct |
11 ms |
12160 KB |
Output is correct |
16 |
Correct |
13 ms |
12032 KB |
Output is correct |
17 |
Correct |
11 ms |
12160 KB |
Output is correct |
18 |
Correct |
11 ms |
12032 KB |
Output is correct |
19 |
Correct |
11 ms |
12032 KB |
Output is correct |
20 |
Correct |
11 ms |
12032 KB |
Output is correct |
21 |
Correct |
11 ms |
12032 KB |
Output is correct |
22 |
Correct |
15 ms |
12288 KB |
Output is correct |
23 |
Correct |
15 ms |
12288 KB |
Output is correct |
24 |
Correct |
14 ms |
12160 KB |
Output is correct |
25 |
Correct |
15 ms |
12160 KB |
Output is correct |
26 |
Correct |
13 ms |
12160 KB |
Output is correct |
27 |
Correct |
14 ms |
12160 KB |
Output is correct |
28 |
Correct |
16 ms |
12160 KB |
Output is correct |
29 |
Correct |
13 ms |
12160 KB |
Output is correct |
30 |
Correct |
13 ms |
12160 KB |
Output is correct |
31 |
Correct |
14 ms |
12288 KB |
Output is correct |
32 |
Correct |
13 ms |
12032 KB |
Output is correct |
33 |
Correct |
13 ms |
12032 KB |
Output is correct |
34 |
Correct |
11 ms |
12160 KB |
Output is correct |
35 |
Correct |
11 ms |
12032 KB |
Output is correct |
36 |
Correct |
12 ms |
12160 KB |
Output is correct |
37 |
Correct |
12 ms |
12160 KB |
Output is correct |
38 |
Correct |
12 ms |
12160 KB |
Output is correct |
39 |
Correct |
11 ms |
12032 KB |
Output is correct |
40 |
Correct |
14 ms |
12032 KB |
Output is correct |
41 |
Correct |
11 ms |
12032 KB |
Output is correct |
42 |
Correct |
12 ms |
12032 KB |
Output is correct |
43 |
Correct |
13 ms |
12160 KB |
Output is correct |
44 |
Correct |
12 ms |
12032 KB |
Output is correct |
45 |
Correct |
14 ms |
12032 KB |
Output is correct |
46 |
Correct |
12 ms |
12160 KB |
Output is correct |
47 |
Correct |
12 ms |
12032 KB |
Output is correct |
48 |
Correct |
14 ms |
12160 KB |
Output is correct |
49 |
Correct |
13 ms |
12160 KB |
Output is correct |
50 |
Correct |
12 ms |
12032 KB |
Output is correct |
51 |
Correct |
13 ms |
12032 KB |
Output is correct |
52 |
Correct |
12 ms |
12032 KB |
Output is correct |
53 |
Correct |
12 ms |
12160 KB |
Output is correct |
54 |
Correct |
13 ms |
12160 KB |
Output is correct |
55 |
Correct |
14 ms |
12160 KB |
Output is correct |
56 |
Correct |
12 ms |
12032 KB |
Output is correct |
57 |
Correct |
12 ms |
12160 KB |
Output is correct |
58 |
Correct |
14 ms |
12288 KB |
Output is correct |
59 |
Correct |
654 ms |
36192 KB |
Output is correct |
60 |
Correct |
827 ms |
38888 KB |
Output is correct |
61 |
Correct |
11 ms |
12032 KB |
Output is correct |
62 |
Correct |
12 ms |
12032 KB |
Output is correct |
63 |
Correct |
592 ms |
33640 KB |
Output is correct |
64 |
Correct |
13 ms |
12416 KB |
Output is correct |
65 |
Correct |
23 ms |
13824 KB |
Output is correct |
66 |
Correct |
153 ms |
25208 KB |
Output is correct |
67 |
Correct |
510 ms |
57720 KB |
Output is correct |
68 |
Correct |
541 ms |
50672 KB |
Output is correct |
69 |
Correct |
31 ms |
13056 KB |
Output is correct |
70 |
Correct |
223 ms |
21356 KB |
Output is correct |
71 |
Correct |
776 ms |
42244 KB |
Output is correct |
72 |
Correct |
734 ms |
40800 KB |
Output is correct |
73 |
Correct |
154 ms |
19188 KB |
Output is correct |
74 |
Correct |
687 ms |
37736 KB |
Output is correct |
75 |
Correct |
80 ms |
15352 KB |
Output is correct |
76 |
Correct |
756 ms |
41808 KB |
Output is correct |
77 |
Correct |
773 ms |
41808 KB |
Output is correct |
78 |
Correct |
54 ms |
15480 KB |
Output is correct |
79 |
Correct |
532 ms |
45176 KB |
Output is correct |
80 |
Correct |
16 ms |
12288 KB |
Output is correct |
81 |
Correct |
229 ms |
21360 KB |
Output is correct |
82 |
Correct |
773 ms |
39656 KB |
Output is correct |
83 |
Correct |
672 ms |
37992 KB |
Output is correct |
84 |
Correct |
766 ms |
37896 KB |
Output is correct |
85 |
Correct |
664 ms |
37736 KB |
Output is correct |
86 |
Correct |
727 ms |
38760 KB |
Output is correct |
87 |
Correct |
744 ms |
39016 KB |
Output is correct |