#include <bits/stdc++.h>
#define int long long
#define pb push_back
using namespace std;
const int maxn = 5e5+10;
const int inf = 1e18;
const int mod = 1e9+7;
int n,cnt,root(-1);
int pendant[2][maxn],deg[maxn]; // 0 -> max , 1 -> sum
vector<int>G[maxn];
vector<int>ans;
void dfs(int v,int par){
for(int b : G[v]){
if(b == par) continue;
dfs(b,v);
pendant[1][v] += pendant[1][b];
pendant[0][v] = max(pendant[0][v],pendant[1][b]);
}
if(deg[v] == 1){
pendant[1][v]++;
}
pendant[0][v] = max(pendant[0][v],cnt-pendant[1][v]);
if(pendant[0][v] <= cnt/2 && root == -1 && deg[v] != 1)
root = v;
}
void dfss(int v,int par){
if(deg[v] == 1)
ans.pb(v);
for(int b : G[v]){
if(b == par) continue;
dfss(b,v);
}
}
int32_t main(){
ios:: sync_with_stdio(0),cin.tie(0),cout.tie(0);
////////////////////////////////////////////////
cin >> n;
for(int i = 1;i<n;i++){
int a,b; cin >> a >> b;
G[a].pb(b),G[b].pb(a);
deg[a]++,deg[b]++;
}
for(int i = 1;i<=n;i++){
if(deg[i] == 1){
cnt++;
}
}
dfs(1,-1);
dfss(root,-1);
int sz = ans.size();
if(sz&1){
cout << (sz+1)/2 << "\n";
int len = (sz+1)/2;
for(int i = 0;i<(sz+1)/2;i++){
cout << ans[i] << " " << ans[min(i+len,sz-1)] << "\n";
}
}
else{
cout << sz/2 << "\n";
int len = sz/2;
for(int i = 0;i<sz/2;i++){
cout << ans[i] << " " << ans[i+len] << "\n";
}
}
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
8 ms |
11980 KB |
Output is correct |
2 |
Correct |
7 ms |
12028 KB |
Output is correct |
3 |
Correct |
7 ms |
11980 KB |
Output is correct |
4 |
Correct |
8 ms |
11980 KB |
Output is correct |
5 |
Correct |
7 ms |
11980 KB |
Output is correct |
6 |
Correct |
8 ms |
11980 KB |
Output is correct |
7 |
Correct |
8 ms |
12020 KB |
Output is correct |
8 |
Correct |
8 ms |
11980 KB |
Output is correct |
9 |
Correct |
7 ms |
11980 KB |
Output is correct |
10 |
Correct |
7 ms |
11980 KB |
Output is correct |
11 |
Correct |
7 ms |
11992 KB |
Output is correct |
12 |
Correct |
7 ms |
11980 KB |
Output is correct |
13 |
Correct |
8 ms |
11980 KB |
Output is correct |
14 |
Correct |
8 ms |
11980 KB |
Output is correct |
15 |
Correct |
7 ms |
11980 KB |
Output is correct |
16 |
Correct |
8 ms |
12020 KB |
Output is correct |
17 |
Correct |
7 ms |
11980 KB |
Output is correct |
18 |
Correct |
7 ms |
11980 KB |
Output is correct |
19 |
Correct |
7 ms |
12084 KB |
Output is correct |
20 |
Correct |
7 ms |
11980 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
8 ms |
11980 KB |
Output is correct |
2 |
Correct |
7 ms |
12028 KB |
Output is correct |
3 |
Correct |
7 ms |
11980 KB |
Output is correct |
4 |
Correct |
8 ms |
11980 KB |
Output is correct |
5 |
Correct |
7 ms |
11980 KB |
Output is correct |
6 |
Correct |
8 ms |
11980 KB |
Output is correct |
7 |
Correct |
8 ms |
12020 KB |
Output is correct |
8 |
Correct |
8 ms |
11980 KB |
Output is correct |
9 |
Correct |
7 ms |
11980 KB |
Output is correct |
10 |
Correct |
7 ms |
11980 KB |
Output is correct |
11 |
Correct |
7 ms |
11992 KB |
Output is correct |
12 |
Correct |
7 ms |
11980 KB |
Output is correct |
13 |
Correct |
8 ms |
11980 KB |
Output is correct |
14 |
Correct |
8 ms |
11980 KB |
Output is correct |
15 |
Correct |
7 ms |
11980 KB |
Output is correct |
16 |
Correct |
8 ms |
12020 KB |
Output is correct |
17 |
Correct |
7 ms |
11980 KB |
Output is correct |
18 |
Correct |
7 ms |
11980 KB |
Output is correct |
19 |
Correct |
7 ms |
12084 KB |
Output is correct |
20 |
Correct |
7 ms |
11980 KB |
Output is correct |
21 |
Correct |
7 ms |
11980 KB |
Output is correct |
22 |
Correct |
8 ms |
12236 KB |
Output is correct |
23 |
Correct |
10 ms |
12244 KB |
Output is correct |
24 |
Correct |
8 ms |
12236 KB |
Output is correct |
25 |
Correct |
8 ms |
12236 KB |
Output is correct |
26 |
Correct |
8 ms |
12200 KB |
Output is correct |
27 |
Correct |
11 ms |
12192 KB |
Output is correct |
28 |
Correct |
9 ms |
12240 KB |
Output is correct |
29 |
Correct |
8 ms |
12112 KB |
Output is correct |
30 |
Correct |
8 ms |
11980 KB |
Output is correct |
31 |
Correct |
8 ms |
12236 KB |
Output is correct |
32 |
Correct |
7 ms |
11980 KB |
Output is correct |
33 |
Correct |
7 ms |
11980 KB |
Output is correct |
34 |
Correct |
8 ms |
11980 KB |
Output is correct |
35 |
Correct |
8 ms |
11980 KB |
Output is correct |
36 |
Correct |
8 ms |
11980 KB |
Output is correct |
37 |
Correct |
8 ms |
12108 KB |
Output is correct |
38 |
Correct |
8 ms |
12180 KB |
Output is correct |
39 |
Correct |
8 ms |
12032 KB |
Output is correct |
40 |
Correct |
8 ms |
11980 KB |
Output is correct |
41 |
Correct |
7 ms |
12088 KB |
Output is correct |
42 |
Correct |
8 ms |
12108 KB |
Output is correct |
43 |
Correct |
8 ms |
12108 KB |
Output is correct |
44 |
Correct |
8 ms |
11980 KB |
Output is correct |
45 |
Correct |
8 ms |
12108 KB |
Output is correct |
46 |
Correct |
8 ms |
12156 KB |
Output is correct |
47 |
Correct |
7 ms |
11980 KB |
Output is correct |
48 |
Correct |
8 ms |
12108 KB |
Output is correct |
49 |
Correct |
8 ms |
12108 KB |
Output is correct |
50 |
Correct |
8 ms |
11980 KB |
Output is correct |
51 |
Correct |
8 ms |
11980 KB |
Output is correct |
52 |
Correct |
9 ms |
12108 KB |
Output is correct |
53 |
Correct |
8 ms |
12108 KB |
Output is correct |
54 |
Correct |
7 ms |
12020 KB |
Output is correct |
55 |
Correct |
7 ms |
12108 KB |
Output is correct |
56 |
Correct |
7 ms |
11980 KB |
Output is correct |
57 |
Correct |
8 ms |
12108 KB |
Output is correct |
58 |
Correct |
10 ms |
12208 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
8 ms |
11980 KB |
Output is correct |
2 |
Correct |
7 ms |
12028 KB |
Output is correct |
3 |
Correct |
7 ms |
11980 KB |
Output is correct |
4 |
Correct |
8 ms |
11980 KB |
Output is correct |
5 |
Correct |
7 ms |
11980 KB |
Output is correct |
6 |
Correct |
8 ms |
11980 KB |
Output is correct |
7 |
Correct |
8 ms |
12020 KB |
Output is correct |
8 |
Correct |
8 ms |
11980 KB |
Output is correct |
9 |
Correct |
7 ms |
11980 KB |
Output is correct |
10 |
Correct |
7 ms |
11980 KB |
Output is correct |
11 |
Correct |
7 ms |
11992 KB |
Output is correct |
12 |
Correct |
7 ms |
11980 KB |
Output is correct |
13 |
Correct |
8 ms |
11980 KB |
Output is correct |
14 |
Correct |
8 ms |
11980 KB |
Output is correct |
15 |
Correct |
7 ms |
11980 KB |
Output is correct |
16 |
Correct |
8 ms |
12020 KB |
Output is correct |
17 |
Correct |
7 ms |
11980 KB |
Output is correct |
18 |
Correct |
7 ms |
11980 KB |
Output is correct |
19 |
Correct |
7 ms |
12084 KB |
Output is correct |
20 |
Correct |
7 ms |
11980 KB |
Output is correct |
21 |
Correct |
7 ms |
11980 KB |
Output is correct |
22 |
Correct |
8 ms |
12236 KB |
Output is correct |
23 |
Correct |
10 ms |
12244 KB |
Output is correct |
24 |
Correct |
8 ms |
12236 KB |
Output is correct |
25 |
Correct |
8 ms |
12236 KB |
Output is correct |
26 |
Correct |
8 ms |
12200 KB |
Output is correct |
27 |
Correct |
11 ms |
12192 KB |
Output is correct |
28 |
Correct |
9 ms |
12240 KB |
Output is correct |
29 |
Correct |
8 ms |
12112 KB |
Output is correct |
30 |
Correct |
8 ms |
11980 KB |
Output is correct |
31 |
Correct |
8 ms |
12236 KB |
Output is correct |
32 |
Correct |
7 ms |
11980 KB |
Output is correct |
33 |
Correct |
7 ms |
11980 KB |
Output is correct |
34 |
Correct |
8 ms |
11980 KB |
Output is correct |
35 |
Correct |
8 ms |
11980 KB |
Output is correct |
36 |
Correct |
8 ms |
11980 KB |
Output is correct |
37 |
Correct |
8 ms |
12108 KB |
Output is correct |
38 |
Correct |
8 ms |
12180 KB |
Output is correct |
39 |
Correct |
8 ms |
12032 KB |
Output is correct |
40 |
Correct |
8 ms |
11980 KB |
Output is correct |
41 |
Correct |
7 ms |
12088 KB |
Output is correct |
42 |
Correct |
8 ms |
12108 KB |
Output is correct |
43 |
Correct |
8 ms |
12108 KB |
Output is correct |
44 |
Correct |
8 ms |
11980 KB |
Output is correct |
45 |
Correct |
8 ms |
12108 KB |
Output is correct |
46 |
Correct |
8 ms |
12156 KB |
Output is correct |
47 |
Correct |
7 ms |
11980 KB |
Output is correct |
48 |
Correct |
8 ms |
12108 KB |
Output is correct |
49 |
Correct |
8 ms |
12108 KB |
Output is correct |
50 |
Correct |
8 ms |
11980 KB |
Output is correct |
51 |
Correct |
8 ms |
11980 KB |
Output is correct |
52 |
Correct |
9 ms |
12108 KB |
Output is correct |
53 |
Correct |
8 ms |
12108 KB |
Output is correct |
54 |
Correct |
7 ms |
12020 KB |
Output is correct |
55 |
Correct |
7 ms |
12108 KB |
Output is correct |
56 |
Correct |
7 ms |
11980 KB |
Output is correct |
57 |
Correct |
8 ms |
12108 KB |
Output is correct |
58 |
Correct |
10 ms |
12208 KB |
Output is correct |
59 |
Correct |
505 ms |
45104 KB |
Output is correct |
60 |
Correct |
596 ms |
48464 KB |
Output is correct |
61 |
Correct |
9 ms |
11980 KB |
Output is correct |
62 |
Correct |
9 ms |
11980 KB |
Output is correct |
63 |
Correct |
406 ms |
40784 KB |
Output is correct |
64 |
Correct |
9 ms |
12620 KB |
Output is correct |
65 |
Correct |
19 ms |
14824 KB |
Output is correct |
66 |
Correct |
198 ms |
35136 KB |
Output is correct |
67 |
Correct |
682 ms |
62916 KB |
Output is correct |
68 |
Correct |
662 ms |
62260 KB |
Output is correct |
69 |
Correct |
16 ms |
13260 KB |
Output is correct |
70 |
Correct |
107 ms |
25028 KB |
Output is correct |
71 |
Correct |
392 ms |
50740 KB |
Output is correct |
72 |
Correct |
428 ms |
49688 KB |
Output is correct |
73 |
Correct |
128 ms |
21624 KB |
Output is correct |
74 |
Correct |
592 ms |
46192 KB |
Output is correct |
75 |
Correct |
39 ms |
16316 KB |
Output is correct |
76 |
Correct |
417 ms |
50532 KB |
Output is correct |
77 |
Correct |
393 ms |
50788 KB |
Output is correct |
78 |
Correct |
41 ms |
16764 KB |
Output is correct |
79 |
Correct |
690 ms |
57512 KB |
Output is correct |
80 |
Correct |
9 ms |
12364 KB |
Output is correct |
81 |
Correct |
135 ms |
24500 KB |
Output is correct |
82 |
Correct |
500 ms |
48488 KB |
Output is correct |
83 |
Correct |
595 ms |
46212 KB |
Output is correct |
84 |
Correct |
593 ms |
46392 KB |
Output is correct |
85 |
Correct |
587 ms |
46256 KB |
Output is correct |
86 |
Correct |
594 ms |
48536 KB |
Output is correct |
87 |
Correct |
625 ms |
48636 KB |
Output is correct |