#include <bits/stdc++.h>
using namespace std;
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
typedef long long ll;
typedef pair<int, int> pii;
const int maxn = 500050;
int n;
vector<int> adj[maxn];
vector<int> leaves;
vector<pii> edges;
void dfs(int u, int p) {
if (adj[u].size() == 1 && adj[u][0] == p) {
leaves.push_back(u);
}
for (int v : adj[u]) {
if (v != p) {
dfs(v, u);
}
}
}
int main() {
ios::sync_with_stdio(false); cin.tie(0);
cin >> n;
for (int i = 0; i < n-1; ++i) {
int a, b;
cin >> a >> b;
adj[a].push_back(b);
adj[b].push_back(a);
}
for (int src = 1; src <= n; ++src) {
if (adj[src].size() > 1) {
dfs(src, -1);
break;
}
}
int k = leaves.size();
for (int i = 0; i < k/2 + !!(k%2); ++i) {
edges.emplace_back(leaves[i], leaves[(i + k/2) % k]);
}
cout << edges.size() << '\n';
for (auto &p : edges) {
cout << p.first << ' ' << p.second << '\n';
}
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
12 ms |
12024 KB |
Output is correct |
2 |
Correct |
12 ms |
12152 KB |
Output is correct |
3 |
Correct |
12 ms |
12024 KB |
Output is correct |
4 |
Correct |
12 ms |
12156 KB |
Output is correct |
5 |
Correct |
12 ms |
12024 KB |
Output is correct |
6 |
Correct |
13 ms |
12284 KB |
Output is correct |
7 |
Correct |
13 ms |
12152 KB |
Output is correct |
8 |
Correct |
13 ms |
12152 KB |
Output is correct |
9 |
Correct |
12 ms |
12152 KB |
Output is correct |
10 |
Correct |
12 ms |
12024 KB |
Output is correct |
11 |
Correct |
12 ms |
12024 KB |
Output is correct |
12 |
Correct |
13 ms |
12152 KB |
Output is correct |
13 |
Correct |
13 ms |
12024 KB |
Output is correct |
14 |
Correct |
13 ms |
12152 KB |
Output is correct |
15 |
Correct |
12 ms |
12152 KB |
Output is correct |
16 |
Correct |
12 ms |
12124 KB |
Output is correct |
17 |
Correct |
13 ms |
12152 KB |
Output is correct |
18 |
Correct |
13 ms |
12152 KB |
Output is correct |
19 |
Correct |
12 ms |
12152 KB |
Output is correct |
20 |
Correct |
12 ms |
12152 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
12 ms |
12024 KB |
Output is correct |
2 |
Correct |
12 ms |
12152 KB |
Output is correct |
3 |
Correct |
12 ms |
12024 KB |
Output is correct |
4 |
Correct |
12 ms |
12156 KB |
Output is correct |
5 |
Correct |
12 ms |
12024 KB |
Output is correct |
6 |
Correct |
13 ms |
12284 KB |
Output is correct |
7 |
Correct |
13 ms |
12152 KB |
Output is correct |
8 |
Correct |
13 ms |
12152 KB |
Output is correct |
9 |
Correct |
12 ms |
12152 KB |
Output is correct |
10 |
Correct |
12 ms |
12024 KB |
Output is correct |
11 |
Correct |
12 ms |
12024 KB |
Output is correct |
12 |
Correct |
13 ms |
12152 KB |
Output is correct |
13 |
Correct |
13 ms |
12024 KB |
Output is correct |
14 |
Correct |
13 ms |
12152 KB |
Output is correct |
15 |
Correct |
12 ms |
12152 KB |
Output is correct |
16 |
Correct |
12 ms |
12124 KB |
Output is correct |
17 |
Correct |
13 ms |
12152 KB |
Output is correct |
18 |
Correct |
13 ms |
12152 KB |
Output is correct |
19 |
Correct |
12 ms |
12152 KB |
Output is correct |
20 |
Correct |
12 ms |
12152 KB |
Output is correct |
21 |
Correct |
13 ms |
12152 KB |
Output is correct |
22 |
Correct |
14 ms |
12284 KB |
Output is correct |
23 |
Correct |
14 ms |
12152 KB |
Output is correct |
24 |
Correct |
13 ms |
12280 KB |
Output is correct |
25 |
Correct |
13 ms |
12156 KB |
Output is correct |
26 |
Correct |
13 ms |
12152 KB |
Output is correct |
27 |
Correct |
13 ms |
12152 KB |
Output is correct |
28 |
Correct |
13 ms |
12152 KB |
Output is correct |
29 |
Correct |
13 ms |
12152 KB |
Output is correct |
30 |
Correct |
13 ms |
12152 KB |
Output is correct |
31 |
Correct |
16 ms |
12152 KB |
Output is correct |
32 |
Correct |
13 ms |
12152 KB |
Output is correct |
33 |
Correct |
12 ms |
12152 KB |
Output is correct |
34 |
Correct |
12 ms |
12152 KB |
Output is correct |
35 |
Correct |
12 ms |
12152 KB |
Output is correct |
36 |
Correct |
12 ms |
12152 KB |
Output is correct |
37 |
Correct |
12 ms |
12152 KB |
Output is correct |
38 |
Correct |
13 ms |
12152 KB |
Output is correct |
39 |
Correct |
12 ms |
12024 KB |
Output is correct |
40 |
Correct |
12 ms |
12152 KB |
Output is correct |
41 |
Correct |
12 ms |
12064 KB |
Output is correct |
42 |
Correct |
13 ms |
12152 KB |
Output is correct |
43 |
Correct |
13 ms |
12152 KB |
Output is correct |
44 |
Correct |
12 ms |
12024 KB |
Output is correct |
45 |
Correct |
13 ms |
12152 KB |
Output is correct |
46 |
Correct |
13 ms |
12152 KB |
Output is correct |
47 |
Correct |
12 ms |
12024 KB |
Output is correct |
48 |
Correct |
13 ms |
12152 KB |
Output is correct |
49 |
Correct |
13 ms |
12152 KB |
Output is correct |
50 |
Correct |
12 ms |
12152 KB |
Output is correct |
51 |
Correct |
12 ms |
12156 KB |
Output is correct |
52 |
Correct |
12 ms |
12160 KB |
Output is correct |
53 |
Correct |
13 ms |
12196 KB |
Output is correct |
54 |
Correct |
12 ms |
12028 KB |
Output is correct |
55 |
Correct |
12 ms |
12124 KB |
Output is correct |
56 |
Correct |
12 ms |
12148 KB |
Output is correct |
57 |
Correct |
12 ms |
12152 KB |
Output is correct |
58 |
Correct |
13 ms |
12152 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
12 ms |
12024 KB |
Output is correct |
2 |
Correct |
12 ms |
12152 KB |
Output is correct |
3 |
Correct |
12 ms |
12024 KB |
Output is correct |
4 |
Correct |
12 ms |
12156 KB |
Output is correct |
5 |
Correct |
12 ms |
12024 KB |
Output is correct |
6 |
Correct |
13 ms |
12284 KB |
Output is correct |
7 |
Correct |
13 ms |
12152 KB |
Output is correct |
8 |
Correct |
13 ms |
12152 KB |
Output is correct |
9 |
Correct |
12 ms |
12152 KB |
Output is correct |
10 |
Correct |
12 ms |
12024 KB |
Output is correct |
11 |
Correct |
12 ms |
12024 KB |
Output is correct |
12 |
Correct |
13 ms |
12152 KB |
Output is correct |
13 |
Correct |
13 ms |
12024 KB |
Output is correct |
14 |
Correct |
13 ms |
12152 KB |
Output is correct |
15 |
Correct |
12 ms |
12152 KB |
Output is correct |
16 |
Correct |
12 ms |
12124 KB |
Output is correct |
17 |
Correct |
13 ms |
12152 KB |
Output is correct |
18 |
Correct |
13 ms |
12152 KB |
Output is correct |
19 |
Correct |
12 ms |
12152 KB |
Output is correct |
20 |
Correct |
12 ms |
12152 KB |
Output is correct |
21 |
Correct |
13 ms |
12152 KB |
Output is correct |
22 |
Correct |
14 ms |
12284 KB |
Output is correct |
23 |
Correct |
14 ms |
12152 KB |
Output is correct |
24 |
Correct |
13 ms |
12280 KB |
Output is correct |
25 |
Correct |
13 ms |
12156 KB |
Output is correct |
26 |
Correct |
13 ms |
12152 KB |
Output is correct |
27 |
Correct |
13 ms |
12152 KB |
Output is correct |
28 |
Correct |
13 ms |
12152 KB |
Output is correct |
29 |
Correct |
13 ms |
12152 KB |
Output is correct |
30 |
Correct |
13 ms |
12152 KB |
Output is correct |
31 |
Correct |
16 ms |
12152 KB |
Output is correct |
32 |
Correct |
13 ms |
12152 KB |
Output is correct |
33 |
Correct |
12 ms |
12152 KB |
Output is correct |
34 |
Correct |
12 ms |
12152 KB |
Output is correct |
35 |
Correct |
12 ms |
12152 KB |
Output is correct |
36 |
Correct |
12 ms |
12152 KB |
Output is correct |
37 |
Correct |
12 ms |
12152 KB |
Output is correct |
38 |
Correct |
13 ms |
12152 KB |
Output is correct |
39 |
Correct |
12 ms |
12024 KB |
Output is correct |
40 |
Correct |
12 ms |
12152 KB |
Output is correct |
41 |
Correct |
12 ms |
12064 KB |
Output is correct |
42 |
Correct |
13 ms |
12152 KB |
Output is correct |
43 |
Correct |
13 ms |
12152 KB |
Output is correct |
44 |
Correct |
12 ms |
12024 KB |
Output is correct |
45 |
Correct |
13 ms |
12152 KB |
Output is correct |
46 |
Correct |
13 ms |
12152 KB |
Output is correct |
47 |
Correct |
12 ms |
12024 KB |
Output is correct |
48 |
Correct |
13 ms |
12152 KB |
Output is correct |
49 |
Correct |
13 ms |
12152 KB |
Output is correct |
50 |
Correct |
12 ms |
12152 KB |
Output is correct |
51 |
Correct |
12 ms |
12156 KB |
Output is correct |
52 |
Correct |
12 ms |
12160 KB |
Output is correct |
53 |
Correct |
13 ms |
12196 KB |
Output is correct |
54 |
Correct |
12 ms |
12028 KB |
Output is correct |
55 |
Correct |
12 ms |
12124 KB |
Output is correct |
56 |
Correct |
12 ms |
12148 KB |
Output is correct |
57 |
Correct |
12 ms |
12152 KB |
Output is correct |
58 |
Correct |
13 ms |
12152 KB |
Output is correct |
59 |
Correct |
401 ms |
37316 KB |
Output is correct |
60 |
Correct |
494 ms |
40164 KB |
Output is correct |
61 |
Correct |
12 ms |
12024 KB |
Output is correct |
62 |
Correct |
13 ms |
12152 KB |
Output is correct |
63 |
Correct |
357 ms |
34844 KB |
Output is correct |
64 |
Correct |
15 ms |
12536 KB |
Output is correct |
65 |
Correct |
26 ms |
13944 KB |
Output is correct |
66 |
Correct |
188 ms |
27896 KB |
Output is correct |
67 |
Correct |
566 ms |
47104 KB |
Output is correct |
68 |
Correct |
558 ms |
48024 KB |
Output is correct |
69 |
Correct |
20 ms |
13048 KB |
Output is correct |
70 |
Correct |
112 ms |
21868 KB |
Output is correct |
71 |
Correct |
378 ms |
43916 KB |
Output is correct |
72 |
Correct |
371 ms |
42588 KB |
Output is correct |
73 |
Correct |
110 ms |
19316 KB |
Output is correct |
74 |
Correct |
500 ms |
39060 KB |
Output is correct |
75 |
Correct |
46 ms |
15476 KB |
Output is correct |
76 |
Correct |
363 ms |
43448 KB |
Output is correct |
77 |
Correct |
352 ms |
43660 KB |
Output is correct |
78 |
Correct |
44 ms |
15608 KB |
Output is correct |
79 |
Correct |
537 ms |
45188 KB |
Output is correct |
80 |
Correct |
15 ms |
12280 KB |
Output is correct |
81 |
Correct |
132 ms |
21872 KB |
Output is correct |
82 |
Correct |
450 ms |
41248 KB |
Output is correct |
83 |
Correct |
495 ms |
38704 KB |
Output is correct |
84 |
Correct |
524 ms |
38668 KB |
Output is correct |
85 |
Correct |
567 ms |
38636 KB |
Output is correct |
86 |
Correct |
548 ms |
40380 KB |
Output is correct |
87 |
Correct |
503 ms |
40104 KB |
Output is correct |