#include<bits/stdc++.h>
#define For(i, a, b) for(int i = a, _b = b; i <= _b; ++i)
#define Ford(i, a, b) for(int i = a, _b = b; i >= _b; --i)
#define FileName "test"
#define ll long long
#define ld long double
#define ull unsigned long
#define Print(x) cerr << #x << "is " << x << '\n';
#define pb push_back
#define X first
#define Y second
//#define Karma
using namespace std;
template<typename T> inline void Cin(T &x)
{
char c;
T sign = 1;
x = 0;
for (c = getchar(); c < '0' || c > '9'; c = getchar())
if (c == '-') sign = -1;
for (; c >= '0' && c <= '9'; c = getchar())
x = x * 10 + c - '0';
x *= sign;
}
template <typename T> inline void Out(T x) {if(x > 9) Out(x / 10); putchar(x % 10 + '0');}
template <typename T> inline void Cout(T x, char c) {if(x < 0) putchar('-'); x = abs(x); Out(x); putchar(c);}
template <typename T, typename... Args> inline void Cin(T& a, Args&... args) {Cin(a);Cin(args...);}
template <typename T, typename... Args> inline void Cout(T a, char c, Args... args) {Cout(a, c);Cout(args...);}
typedef pair<int, int> pii;
typedef pair<ll, int> plli;
const int N = 2e5 + 7;
int n, u, v;
vector<int> res, a[N];
void Enter()
{
Cin(n);
For(i, 2, n)
{
Cin(u, v);
a[u].pb(v), a[v].pb(u);
}
}
void DFS(int u, int par)
{
for(int v: a[u])
if(v != par)
DFS(v, u);
if(a[u].size() == 1) res.pb(u);
}
void Solve()
{
For(i, 1, n) if(a[i].size() > 1) {DFS(i, i); break;}
int sz = res.size();
cout << (sz + 1) / 2 << '\n';
for(int i = 0; i * 2 + 1 < sz; ++i) cout << res[i] << ' ' << res[i + (sz + 1) / 2] << '\n';
if(sz & 1) cout << res[sz / 2] << ' ' << res[0] << '\n';
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
#ifdef Karma
freopen(FileName".inp", "r", stdin);
freopen(FileName".out", "w", stdout);
#endif // Karma
Enter();
Solve();
return 0;
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
5 ms |
5112 KB |
Output is correct |
2 |
Correct |
5 ms |
4984 KB |
Output is correct |
3 |
Correct |
5 ms |
4984 KB |
Output is correct |
4 |
Correct |
5 ms |
5112 KB |
Output is correct |
5 |
Correct |
6 ms |
5112 KB |
Output is correct |
6 |
Correct |
5 ms |
4984 KB |
Output is correct |
7 |
Correct |
6 ms |
5112 KB |
Output is correct |
8 |
Correct |
5 ms |
5112 KB |
Output is correct |
9 |
Correct |
5 ms |
5112 KB |
Output is correct |
10 |
Correct |
5 ms |
4988 KB |
Output is correct |
11 |
Correct |
5 ms |
5112 KB |
Output is correct |
12 |
Correct |
5 ms |
5112 KB |
Output is correct |
13 |
Correct |
5 ms |
4984 KB |
Output is correct |
14 |
Correct |
5 ms |
5112 KB |
Output is correct |
15 |
Correct |
6 ms |
5112 KB |
Output is correct |
16 |
Correct |
6 ms |
4988 KB |
Output is correct |
17 |
Correct |
5 ms |
5112 KB |
Output is correct |
18 |
Correct |
5 ms |
5112 KB |
Output is correct |
19 |
Correct |
6 ms |
5112 KB |
Output is correct |
20 |
Correct |
6 ms |
5112 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
5 ms |
5112 KB |
Output is correct |
2 |
Correct |
5 ms |
4984 KB |
Output is correct |
3 |
Correct |
5 ms |
4984 KB |
Output is correct |
4 |
Correct |
5 ms |
5112 KB |
Output is correct |
5 |
Correct |
6 ms |
5112 KB |
Output is correct |
6 |
Correct |
5 ms |
4984 KB |
Output is correct |
7 |
Correct |
6 ms |
5112 KB |
Output is correct |
8 |
Correct |
5 ms |
5112 KB |
Output is correct |
9 |
Correct |
5 ms |
5112 KB |
Output is correct |
10 |
Correct |
5 ms |
4988 KB |
Output is correct |
11 |
Correct |
5 ms |
5112 KB |
Output is correct |
12 |
Correct |
5 ms |
5112 KB |
Output is correct |
13 |
Correct |
5 ms |
4984 KB |
Output is correct |
14 |
Correct |
5 ms |
5112 KB |
Output is correct |
15 |
Correct |
6 ms |
5112 KB |
Output is correct |
16 |
Correct |
6 ms |
4988 KB |
Output is correct |
17 |
Correct |
5 ms |
5112 KB |
Output is correct |
18 |
Correct |
5 ms |
5112 KB |
Output is correct |
19 |
Correct |
6 ms |
5112 KB |
Output is correct |
20 |
Correct |
6 ms |
5112 KB |
Output is correct |
21 |
Correct |
5 ms |
4984 KB |
Output is correct |
22 |
Correct |
6 ms |
5112 KB |
Output is correct |
23 |
Correct |
6 ms |
5116 KB |
Output is correct |
24 |
Correct |
6 ms |
5112 KB |
Output is correct |
25 |
Correct |
6 ms |
5112 KB |
Output is correct |
26 |
Correct |
5 ms |
5116 KB |
Output is correct |
27 |
Correct |
5 ms |
5112 KB |
Output is correct |
28 |
Correct |
5 ms |
5112 KB |
Output is correct |
29 |
Correct |
5 ms |
5112 KB |
Output is correct |
30 |
Correct |
5 ms |
5084 KB |
Output is correct |
31 |
Correct |
6 ms |
5112 KB |
Output is correct |
32 |
Correct |
5 ms |
4984 KB |
Output is correct |
33 |
Correct |
5 ms |
5112 KB |
Output is correct |
34 |
Correct |
5 ms |
5112 KB |
Output is correct |
35 |
Correct |
5 ms |
5116 KB |
Output is correct |
36 |
Correct |
5 ms |
5116 KB |
Output is correct |
37 |
Correct |
6 ms |
5084 KB |
Output is correct |
38 |
Correct |
6 ms |
5112 KB |
Output is correct |
39 |
Correct |
6 ms |
4984 KB |
Output is correct |
40 |
Correct |
6 ms |
4984 KB |
Output is correct |
41 |
Correct |
5 ms |
4984 KB |
Output is correct |
42 |
Correct |
5 ms |
4984 KB |
Output is correct |
43 |
Correct |
6 ms |
5112 KB |
Output is correct |
44 |
Correct |
5 ms |
4984 KB |
Output is correct |
45 |
Correct |
5 ms |
5112 KB |
Output is correct |
46 |
Correct |
5 ms |
5112 KB |
Output is correct |
47 |
Correct |
5 ms |
5112 KB |
Output is correct |
48 |
Correct |
6 ms |
4984 KB |
Output is correct |
49 |
Correct |
5 ms |
5112 KB |
Output is correct |
50 |
Correct |
5 ms |
4984 KB |
Output is correct |
51 |
Correct |
5 ms |
4984 KB |
Output is correct |
52 |
Correct |
5 ms |
4984 KB |
Output is correct |
53 |
Correct |
5 ms |
5112 KB |
Output is correct |
54 |
Correct |
5 ms |
4984 KB |
Output is correct |
55 |
Correct |
5 ms |
5056 KB |
Output is correct |
56 |
Correct |
5 ms |
5112 KB |
Output is correct |
57 |
Correct |
5 ms |
5112 KB |
Output is correct |
58 |
Correct |
5 ms |
5112 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
5 ms |
5112 KB |
Output is correct |
2 |
Correct |
5 ms |
4984 KB |
Output is correct |
3 |
Correct |
5 ms |
4984 KB |
Output is correct |
4 |
Correct |
5 ms |
5112 KB |
Output is correct |
5 |
Correct |
6 ms |
5112 KB |
Output is correct |
6 |
Correct |
5 ms |
4984 KB |
Output is correct |
7 |
Correct |
6 ms |
5112 KB |
Output is correct |
8 |
Correct |
5 ms |
5112 KB |
Output is correct |
9 |
Correct |
5 ms |
5112 KB |
Output is correct |
10 |
Correct |
5 ms |
4988 KB |
Output is correct |
11 |
Correct |
5 ms |
5112 KB |
Output is correct |
12 |
Correct |
5 ms |
5112 KB |
Output is correct |
13 |
Correct |
5 ms |
4984 KB |
Output is correct |
14 |
Correct |
5 ms |
5112 KB |
Output is correct |
15 |
Correct |
6 ms |
5112 KB |
Output is correct |
16 |
Correct |
6 ms |
4988 KB |
Output is correct |
17 |
Correct |
5 ms |
5112 KB |
Output is correct |
18 |
Correct |
5 ms |
5112 KB |
Output is correct |
19 |
Correct |
6 ms |
5112 KB |
Output is correct |
20 |
Correct |
6 ms |
5112 KB |
Output is correct |
21 |
Correct |
5 ms |
4984 KB |
Output is correct |
22 |
Correct |
6 ms |
5112 KB |
Output is correct |
23 |
Correct |
6 ms |
5116 KB |
Output is correct |
24 |
Correct |
6 ms |
5112 KB |
Output is correct |
25 |
Correct |
6 ms |
5112 KB |
Output is correct |
26 |
Correct |
5 ms |
5116 KB |
Output is correct |
27 |
Correct |
5 ms |
5112 KB |
Output is correct |
28 |
Correct |
5 ms |
5112 KB |
Output is correct |
29 |
Correct |
5 ms |
5112 KB |
Output is correct |
30 |
Correct |
5 ms |
5084 KB |
Output is correct |
31 |
Correct |
6 ms |
5112 KB |
Output is correct |
32 |
Correct |
5 ms |
4984 KB |
Output is correct |
33 |
Correct |
5 ms |
5112 KB |
Output is correct |
34 |
Correct |
5 ms |
5112 KB |
Output is correct |
35 |
Correct |
5 ms |
5116 KB |
Output is correct |
36 |
Correct |
5 ms |
5116 KB |
Output is correct |
37 |
Correct |
6 ms |
5084 KB |
Output is correct |
38 |
Correct |
6 ms |
5112 KB |
Output is correct |
39 |
Correct |
6 ms |
4984 KB |
Output is correct |
40 |
Correct |
6 ms |
4984 KB |
Output is correct |
41 |
Correct |
5 ms |
4984 KB |
Output is correct |
42 |
Correct |
5 ms |
4984 KB |
Output is correct |
43 |
Correct |
6 ms |
5112 KB |
Output is correct |
44 |
Correct |
5 ms |
4984 KB |
Output is correct |
45 |
Correct |
5 ms |
5112 KB |
Output is correct |
46 |
Correct |
5 ms |
5112 KB |
Output is correct |
47 |
Correct |
5 ms |
5112 KB |
Output is correct |
48 |
Correct |
6 ms |
4984 KB |
Output is correct |
49 |
Correct |
5 ms |
5112 KB |
Output is correct |
50 |
Correct |
5 ms |
4984 KB |
Output is correct |
51 |
Correct |
5 ms |
4984 KB |
Output is correct |
52 |
Correct |
5 ms |
4984 KB |
Output is correct |
53 |
Correct |
5 ms |
5112 KB |
Output is correct |
54 |
Correct |
5 ms |
4984 KB |
Output is correct |
55 |
Correct |
5 ms |
5056 KB |
Output is correct |
56 |
Correct |
5 ms |
5112 KB |
Output is correct |
57 |
Correct |
5 ms |
5112 KB |
Output is correct |
58 |
Correct |
5 ms |
5112 KB |
Output is correct |
59 |
Runtime error |
10 ms |
9848 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
60 |
Halted |
0 ms |
0 KB |
- |