#include <bits/stdc++.h>
#pragma GCC target("sse,sse2")
#pragma GCC optimize("unroll-loops,O3")
#define rep(i,l,r) for (int i = l; i < r; i++)
#define repr(i,r,l) for (int i = r; i >= l; i--)
#define X first
#define Y second
#define all(x) (x).begin() , (x).end()
#define pb push_back
#define endl '\n'
#define debug(x) cerr << #x << " : " << x << endl;
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pll;
constexpr int N = 5e5+20,mod = 1e9+7,inf = 1e9+10;
inline int mkay(int a,int b){
if (a+b >= mod) return a+b-mod;
if (a+b < 0) return a+b+mod;
return a+b;
}
inline int poww(int a,int k){
if (k < 0) return 0;
int z = 1;
while (k){
if (k&1) z = 1ll*z*a%mod;
a = 1ll*a*a%mod;
k /= 2;
}
return z;
}
vector<int> adj[N],ve;
int tin[N],T;
bool cmp(int u,int v){
return (tin[u] < tin[v]);
}
void dfs(int v,int p){
tin[v] = T++;
for(int u : adj[v]) if (u != p) dfs(u,v);
}
int main(){
ios_base :: sync_with_stdio(0); cin.tie(0);
int n,ans = 0;
cin >> n;
rep(i,1,n){
int u,v;
cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
dfs(1,0);
rep(i,1,n+1) if (adj[i].size() == 1){
ans++;
ve.pb(i);
}
int t = (ans+1)/2;
cout << t << endl;
sort(all(ve),cmp);
rep(i,0,ans){
if (i >= t) break;
if (i+t == ans){
cout << ve[i] << ' ' << ve[0] << endl;
break;
}
cout << ve[i] << ' ' << ve[i+t] << endl;
}
}
# |
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 |
6 ms |
11988 KB |
Output is correct |
4 |
Correct |
7 ms |
11964 KB |
Output is correct |
5 |
Correct |
7 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
7 ms |
11988 KB |
Output is correct |
8 |
Correct |
7 ms |
11988 KB |
Output is correct |
9 |
Correct |
6 ms |
11988 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
6 ms |
11988 KB |
Output is correct |
12 |
Correct |
6 ms |
11988 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 |
12064 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
7 ms |
11988 KB |
Output is correct |
18 |
Correct |
7 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
11960 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 |
6 ms |
11988 KB |
Output is correct |
4 |
Correct |
7 ms |
11964 KB |
Output is correct |
5 |
Correct |
7 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
7 ms |
11988 KB |
Output is correct |
8 |
Correct |
7 ms |
11988 KB |
Output is correct |
9 |
Correct |
6 ms |
11988 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
6 ms |
11988 KB |
Output is correct |
12 |
Correct |
6 ms |
11988 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 |
12064 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
7 ms |
11988 KB |
Output is correct |
18 |
Correct |
7 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
11960 KB |
Output is correct |
20 |
Correct |
6 ms |
11988 KB |
Output is correct |
21 |
Correct |
7 ms |
11988 KB |
Output is correct |
22 |
Correct |
7 ms |
12116 KB |
Output is correct |
23 |
Correct |
6 ms |
12116 KB |
Output is correct |
24 |
Correct |
7 ms |
12116 KB |
Output is correct |
25 |
Correct |
6 ms |
12116 KB |
Output is correct |
26 |
Correct |
8 ms |
12116 KB |
Output is correct |
27 |
Correct |
8 ms |
12116 KB |
Output is correct |
28 |
Correct |
7 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 |
7 ms |
12116 KB |
Output is correct |
32 |
Correct |
6 ms |
11988 KB |
Output is correct |
33 |
Correct |
8 ms |
11988 KB |
Output is correct |
34 |
Correct |
7 ms |
11988 KB |
Output is correct |
35 |
Correct |
6 ms |
11988 KB |
Output is correct |
36 |
Correct |
7 ms |
12064 KB |
Output is correct |
37 |
Correct |
6 ms |
11988 KB |
Output is correct |
38 |
Correct |
6 ms |
12116 KB |
Output is correct |
39 |
Correct |
6 ms |
11988 KB |
Output is correct |
40 |
Correct |
8 ms |
12068 KB |
Output is correct |
41 |
Correct |
7 ms |
11988 KB |
Output is correct |
42 |
Correct |
8 ms |
12068 KB |
Output is correct |
43 |
Correct |
6 ms |
12116 KB |
Output is correct |
44 |
Correct |
6 ms |
11988 KB |
Output is correct |
45 |
Correct |
8 ms |
11988 KB |
Output is correct |
46 |
Correct |
6 ms |
11988 KB |
Output is correct |
47 |
Correct |
6 ms |
11988 KB |
Output is correct |
48 |
Correct |
9 ms |
12084 KB |
Output is correct |
49 |
Correct |
7 ms |
12116 KB |
Output is correct |
50 |
Correct |
6 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 |
6 ms |
11988 KB |
Output is correct |
54 |
Correct |
6 ms |
11988 KB |
Output is correct |
55 |
Correct |
6 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 |
7 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 |
6 ms |
11988 KB |
Output is correct |
4 |
Correct |
7 ms |
11964 KB |
Output is correct |
5 |
Correct |
7 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
11988 KB |
Output is correct |
7 |
Correct |
7 ms |
11988 KB |
Output is correct |
8 |
Correct |
7 ms |
11988 KB |
Output is correct |
9 |
Correct |
6 ms |
11988 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
6 ms |
11988 KB |
Output is correct |
12 |
Correct |
6 ms |
11988 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 |
12064 KB |
Output is correct |
16 |
Correct |
6 ms |
11988 KB |
Output is correct |
17 |
Correct |
7 ms |
11988 KB |
Output is correct |
18 |
Correct |
7 ms |
11988 KB |
Output is correct |
19 |
Correct |
6 ms |
11960 KB |
Output is correct |
20 |
Correct |
6 ms |
11988 KB |
Output is correct |
21 |
Correct |
7 ms |
11988 KB |
Output is correct |
22 |
Correct |
7 ms |
12116 KB |
Output is correct |
23 |
Correct |
6 ms |
12116 KB |
Output is correct |
24 |
Correct |
7 ms |
12116 KB |
Output is correct |
25 |
Correct |
6 ms |
12116 KB |
Output is correct |
26 |
Correct |
8 ms |
12116 KB |
Output is correct |
27 |
Correct |
8 ms |
12116 KB |
Output is correct |
28 |
Correct |
7 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 |
7 ms |
12116 KB |
Output is correct |
32 |
Correct |
6 ms |
11988 KB |
Output is correct |
33 |
Correct |
8 ms |
11988 KB |
Output is correct |
34 |
Correct |
7 ms |
11988 KB |
Output is correct |
35 |
Correct |
6 ms |
11988 KB |
Output is correct |
36 |
Correct |
7 ms |
12064 KB |
Output is correct |
37 |
Correct |
6 ms |
11988 KB |
Output is correct |
38 |
Correct |
6 ms |
12116 KB |
Output is correct |
39 |
Correct |
6 ms |
11988 KB |
Output is correct |
40 |
Correct |
8 ms |
12068 KB |
Output is correct |
41 |
Correct |
7 ms |
11988 KB |
Output is correct |
42 |
Correct |
8 ms |
12068 KB |
Output is correct |
43 |
Correct |
6 ms |
12116 KB |
Output is correct |
44 |
Correct |
6 ms |
11988 KB |
Output is correct |
45 |
Correct |
8 ms |
11988 KB |
Output is correct |
46 |
Correct |
6 ms |
11988 KB |
Output is correct |
47 |
Correct |
6 ms |
11988 KB |
Output is correct |
48 |
Correct |
9 ms |
12084 KB |
Output is correct |
49 |
Correct |
7 ms |
12116 KB |
Output is correct |
50 |
Correct |
6 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 |
6 ms |
11988 KB |
Output is correct |
54 |
Correct |
6 ms |
11988 KB |
Output is correct |
55 |
Correct |
6 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 |
7 ms |
12116 KB |
Output is correct |
59 |
Correct |
330 ms |
31748 KB |
Output is correct |
60 |
Correct |
410 ms |
34072 KB |
Output is correct |
61 |
Correct |
6 ms |
11988 KB |
Output is correct |
62 |
Correct |
7 ms |
11988 KB |
Output is correct |
63 |
Correct |
290 ms |
29860 KB |
Output is correct |
64 |
Correct |
8 ms |
12244 KB |
Output is correct |
65 |
Correct |
14 ms |
13268 KB |
Output is correct |
66 |
Correct |
131 ms |
22524 KB |
Output is correct |
67 |
Correct |
388 ms |
36252 KB |
Output is correct |
68 |
Correct |
399 ms |
36816 KB |
Output is correct |
69 |
Correct |
13 ms |
12756 KB |
Output is correct |
70 |
Correct |
109 ms |
19752 KB |
Output is correct |
71 |
Correct |
297 ms |
37096 KB |
Output is correct |
72 |
Correct |
344 ms |
36272 KB |
Output is correct |
73 |
Correct |
88 ms |
17860 KB |
Output is correct |
74 |
Correct |
406 ms |
33024 KB |
Output is correct |
75 |
Correct |
37 ms |
14804 KB |
Output is correct |
76 |
Correct |
314 ms |
36696 KB |
Output is correct |
77 |
Correct |
307 ms |
37132 KB |
Output is correct |
78 |
Correct |
29 ms |
14560 KB |
Output is correct |
79 |
Correct |
413 ms |
35236 KB |
Output is correct |
80 |
Correct |
8 ms |
12244 KB |
Output is correct |
81 |
Correct |
122 ms |
19844 KB |
Output is correct |
82 |
Correct |
352 ms |
35056 KB |
Output is correct |
83 |
Correct |
421 ms |
32988 KB |
Output is correct |
84 |
Correct |
395 ms |
32920 KB |
Output is correct |
85 |
Correct |
386 ms |
32932 KB |
Output is correct |
86 |
Correct |
383 ms |
34080 KB |
Output is correct |
87 |
Correct |
466 ms |
34188 KB |
Output is correct |