#include<iostream>
#include<vector>
#include<algorithm>
#include<cstring>
#include<utility>
#define pb push_back
#define pii pair<int, int>
#define F first
#define S second
using namespace std;
const int N = (int)5e5 + 5;
int n , u, v, ind[N], _id = 0, root = 1;
vector<int> leafs;
vector<pii> ret;
vector<int> adj[N];
void dfs(int v,int p){
ind[v] = _id ++;
for(auto u : adj[v])if(u != p)dfs(u , v);
}
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n;
for(int i = 1; i < n ; i ++){
cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
for(int i = 1; i <= n; i ++)if(adj[i].size() > 1)root = i;
dfs(root, root);
for(int i = 1; i <= n; i ++){
if(adj[i].size() == 1)ret.pb({ind[i], i});
}
sort(ret.begin(), ret.end());
int sz= ret.size();
cout << ((sz + 1) >> 1) << endl;
for(int i = 0; i < sz/2; i ++) cout << ret[i].S << " " << ret[i + (sz+1)/2].S << endl;
if(sz&1) cout << ret[sz/2].S << " " << root << endl;
exit(0);
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
6 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
11988 KB |
Output is correct |
3 |
Correct |
8 ms |
11988 KB |
Output is correct |
4 |
Correct |
7 ms |
11992 KB |
Output is correct |
5 |
Correct |
6 ms |
11944 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
6 ms |
11988 KB |
Output is correct |
8 |
Correct |
7 ms |
11988 KB |
Output is correct |
9 |
Correct |
9 ms |
12032 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
8 ms |
11964 KB |
Output is correct |
12 |
Correct |
6 ms |
12040 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
6 ms |
11988 KB |
Output is correct |
15 |
Correct |
7 ms |
11988 KB |
Output is correct |
16 |
Correct |
7 ms |
12028 KB |
Output is correct |
17 |
Correct |
6 ms |
12064 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
11988 KB |
Output is correct |
20 |
Correct |
6 ms |
11988 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
6 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
11988 KB |
Output is correct |
3 |
Correct |
8 ms |
11988 KB |
Output is correct |
4 |
Correct |
7 ms |
11992 KB |
Output is correct |
5 |
Correct |
6 ms |
11944 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
6 ms |
11988 KB |
Output is correct |
8 |
Correct |
7 ms |
11988 KB |
Output is correct |
9 |
Correct |
9 ms |
12032 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
8 ms |
11964 KB |
Output is correct |
12 |
Correct |
6 ms |
12040 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
6 ms |
11988 KB |
Output is correct |
15 |
Correct |
7 ms |
11988 KB |
Output is correct |
16 |
Correct |
7 ms |
12028 KB |
Output is correct |
17 |
Correct |
6 ms |
12064 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
11988 KB |
Output is correct |
20 |
Correct |
6 ms |
11988 KB |
Output is correct |
21 |
Correct |
6 ms |
11988 KB |
Output is correct |
22 |
Correct |
8 ms |
12116 KB |
Output is correct |
23 |
Correct |
8 ms |
12116 KB |
Output is correct |
24 |
Correct |
8 ms |
12116 KB |
Output is correct |
25 |
Correct |
8 ms |
12116 KB |
Output is correct |
26 |
Correct |
7 ms |
12116 KB |
Output is correct |
27 |
Correct |
8 ms |
12116 KB |
Output is correct |
28 |
Correct |
8 ms |
12116 KB |
Output is correct |
29 |
Correct |
7 ms |
12116 KB |
Output is correct |
30 |
Correct |
6 ms |
11988 KB |
Output is correct |
31 |
Correct |
8 ms |
12116 KB |
Output is correct |
32 |
Correct |
6 ms |
11988 KB |
Output is correct |
33 |
Correct |
7 ms |
11972 KB |
Output is correct |
34 |
Correct |
6 ms |
11988 KB |
Output is correct |
35 |
Correct |
8 ms |
12060 KB |
Output is correct |
36 |
Correct |
8 ms |
11988 KB |
Output is correct |
37 |
Correct |
8 ms |
11988 KB |
Output is correct |
38 |
Correct |
6 ms |
12060 KB |
Output is correct |
39 |
Correct |
6 ms |
11988 KB |
Output is correct |
40 |
Correct |
7 ms |
12024 KB |
Output is correct |
41 |
Correct |
9 ms |
11988 KB |
Output is correct |
42 |
Correct |
8 ms |
11988 KB |
Output is correct |
43 |
Correct |
7 ms |
12116 KB |
Output is correct |
44 |
Correct |
6 ms |
11988 KB |
Output is correct |
45 |
Correct |
7 ms |
11988 KB |
Output is correct |
46 |
Correct |
7 ms |
11988 KB |
Output is correct |
47 |
Correct |
6 ms |
11988 KB |
Output is correct |
48 |
Correct |
6 ms |
11988 KB |
Output is correct |
49 |
Correct |
7 ms |
12116 KB |
Output is correct |
50 |
Correct |
8 ms |
11988 KB |
Output is correct |
51 |
Correct |
6 ms |
11988 KB |
Output is correct |
52 |
Correct |
6 ms |
11988 KB |
Output is correct |
53 |
Correct |
7 ms |
12116 KB |
Output is correct |
54 |
Correct |
6 ms |
11988 KB |
Output is correct |
55 |
Correct |
7 ms |
11988 KB |
Output is correct |
56 |
Correct |
6 ms |
11988 KB |
Output is correct |
57 |
Correct |
6 ms |
11988 KB |
Output is correct |
58 |
Correct |
8 ms |
12116 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
6 ms |
11988 KB |
Output is correct |
2 |
Correct |
6 ms |
11988 KB |
Output is correct |
3 |
Correct |
8 ms |
11988 KB |
Output is correct |
4 |
Correct |
7 ms |
11992 KB |
Output is correct |
5 |
Correct |
6 ms |
11944 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
6 ms |
11988 KB |
Output is correct |
8 |
Correct |
7 ms |
11988 KB |
Output is correct |
9 |
Correct |
9 ms |
12032 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
8 ms |
11964 KB |
Output is correct |
12 |
Correct |
6 ms |
12040 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
6 ms |
11988 KB |
Output is correct |
15 |
Correct |
7 ms |
11988 KB |
Output is correct |
16 |
Correct |
7 ms |
12028 KB |
Output is correct |
17 |
Correct |
6 ms |
12064 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
11988 KB |
Output is correct |
20 |
Correct |
6 ms |
11988 KB |
Output is correct |
21 |
Correct |
6 ms |
11988 KB |
Output is correct |
22 |
Correct |
8 ms |
12116 KB |
Output is correct |
23 |
Correct |
8 ms |
12116 KB |
Output is correct |
24 |
Correct |
8 ms |
12116 KB |
Output is correct |
25 |
Correct |
8 ms |
12116 KB |
Output is correct |
26 |
Correct |
7 ms |
12116 KB |
Output is correct |
27 |
Correct |
8 ms |
12116 KB |
Output is correct |
28 |
Correct |
8 ms |
12116 KB |
Output is correct |
29 |
Correct |
7 ms |
12116 KB |
Output is correct |
30 |
Correct |
6 ms |
11988 KB |
Output is correct |
31 |
Correct |
8 ms |
12116 KB |
Output is correct |
32 |
Correct |
6 ms |
11988 KB |
Output is correct |
33 |
Correct |
7 ms |
11972 KB |
Output is correct |
34 |
Correct |
6 ms |
11988 KB |
Output is correct |
35 |
Correct |
8 ms |
12060 KB |
Output is correct |
36 |
Correct |
8 ms |
11988 KB |
Output is correct |
37 |
Correct |
8 ms |
11988 KB |
Output is correct |
38 |
Correct |
6 ms |
12060 KB |
Output is correct |
39 |
Correct |
6 ms |
11988 KB |
Output is correct |
40 |
Correct |
7 ms |
12024 KB |
Output is correct |
41 |
Correct |
9 ms |
11988 KB |
Output is correct |
42 |
Correct |
8 ms |
11988 KB |
Output is correct |
43 |
Correct |
7 ms |
12116 KB |
Output is correct |
44 |
Correct |
6 ms |
11988 KB |
Output is correct |
45 |
Correct |
7 ms |
11988 KB |
Output is correct |
46 |
Correct |
7 ms |
11988 KB |
Output is correct |
47 |
Correct |
6 ms |
11988 KB |
Output is correct |
48 |
Correct |
6 ms |
11988 KB |
Output is correct |
49 |
Correct |
7 ms |
12116 KB |
Output is correct |
50 |
Correct |
8 ms |
11988 KB |
Output is correct |
51 |
Correct |
6 ms |
11988 KB |
Output is correct |
52 |
Correct |
6 ms |
11988 KB |
Output is correct |
53 |
Correct |
7 ms |
12116 KB |
Output is correct |
54 |
Correct |
6 ms |
11988 KB |
Output is correct |
55 |
Correct |
7 ms |
11988 KB |
Output is correct |
56 |
Correct |
6 ms |
11988 KB |
Output is correct |
57 |
Correct |
6 ms |
11988 KB |
Output is correct |
58 |
Correct |
8 ms |
12116 KB |
Output is correct |
59 |
Correct |
482 ms |
32976 KB |
Output is correct |
60 |
Correct |
547 ms |
35320 KB |
Output is correct |
61 |
Correct |
6 ms |
11988 KB |
Output is correct |
62 |
Correct |
6 ms |
11988 KB |
Output is correct |
63 |
Correct |
485 ms |
30952 KB |
Output is correct |
64 |
Correct |
10 ms |
12244 KB |
Output is correct |
65 |
Correct |
18 ms |
13180 KB |
Output is correct |
66 |
Correct |
102 ms |
20812 KB |
Output is correct |
67 |
Correct |
423 ms |
40912 KB |
Output is correct |
68 |
Correct |
447 ms |
37976 KB |
Output is correct |
69 |
Correct |
22 ms |
12936 KB |
Output is correct |
70 |
Correct |
157 ms |
20492 KB |
Output is correct |
71 |
Correct |
568 ms |
38972 KB |
Output is correct |
72 |
Correct |
536 ms |
38100 KB |
Output is correct |
73 |
Correct |
109 ms |
18220 KB |
Output is correct |
74 |
Correct |
552 ms |
33980 KB |
Output is correct |
75 |
Correct |
58 ms |
15016 KB |
Output is correct |
76 |
Correct |
590 ms |
38576 KB |
Output is correct |
77 |
Correct |
563 ms |
39080 KB |
Output is correct |
78 |
Correct |
35 ms |
14676 KB |
Output is correct |
79 |
Correct |
376 ms |
34704 KB |
Output is correct |
80 |
Correct |
9 ms |
12244 KB |
Output is correct |
81 |
Correct |
160 ms |
20356 KB |
Output is correct |
82 |
Correct |
558 ms |
36440 KB |
Output is correct |
83 |
Correct |
534 ms |
34000 KB |
Output is correct |
84 |
Correct |
531 ms |
33980 KB |
Output is correct |
85 |
Correct |
529 ms |
34112 KB |
Output is correct |
86 |
Correct |
584 ms |
35460 KB |
Output is correct |
87 |
Correct |
558 ms |
35496 KB |
Output is correct |