/*CP template version 3.0 - Laconic*/
#include <bits/stdc++.h>
#define ii pair<int, int>
#define fs first
#define sc second
//use struct instead of pair<int, ii>
#define int long long
#define show(v) {for (auto i : v) cout << i << " "; cout << endl;}
#define showlr(v, l, r) {for (int i = l; i <= r; i++) cout << v[i] << " "; cout << endl;}
#define all(v) v.begin(), v.end()
#define SUnique(v) {sort(all(v)); v.erase(unique(all(v)), v.end());}
#define forlr(i, l, r) for (int i = l; i <= r; i++)
#define forrl(i, r, l) for (int i = r; i >= l; i--)
#pragma GCC Optimize("O2")
#define endl "\n"
#define precise(x) cout << fixed << setprecision(x);
using namespace std;
const int N = 5e5 + 100;
const int MOD = 1e9 + 7;
const int INF = 1e9;
const int LOG = 25;
const long long LINF = 1e15 + 100;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, -1, 0, 1};
ostream& operator << (ostream &os, ii a) {
os << a.fs << ' ' << a.sc;
return os;
}
int binPow(int a, int b, int m = LLONG_MAX) {
int prod = 1;
a %= m;
while (b) {
if (b & 1) prod = prod * a % m;
a = a * a % m;
b /= 2;
}
return prod;
}
void setIO(string s) {
if (s.empty()) return;
freopen((s + ".inp").c_str(), "r", stdin);
freopen((s + ".out").c_str(), "w", stdout);
}
//Try Brute Force (maybe there is a pattern)
//Try DP (Weird constraints (sum of all elements <= 10000), small constraints)
//Try Graph (a pair of number, condition between elements)
//Try Geometry (Same as graph, for coordinate)
//Try switching between problem
//Put down what you have on paper
//IMPORTANT: WRITE DOWN THE FORMULA
int n, m, q, k;
int arr[N];
vector<int> adj[N];
mt19937 rng(chrono::steady_clock().now().time_since_epoch().count());
vector<int> leaf;
void dfs(int u, int pre) {
if (adj[u].size() == 1) {
leaf.push_back(u);
if (u != pre) return;
}
for (int v : adj[u]) {
if (v == pre) continue;
dfs(v, u);
}
}
int deg[N];
ii edges[N];
void solve() {
cin >> n;
forlr(i, 1, n - 1) {
int u, v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
dfs(1, 1);
vector<ii> res;
int sz = leaf.size();
if (sz == 2) {
cout << 1 << endl;
cout << leaf[0] << " " << leaf[1] << endl;
return;
}
if (sz <= 1) {
cout << 0 << endl;
return;
}
forlr(i, 0, (sz - 1) / 2) res.push_back({leaf[i], leaf[i + sz / 2]});
cout << res.size() << endl;
for (ii i : res) cout << i << endl;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int T = 1;
bool multiTest = 0;
if (multiTest) cin >> T;
while (T--) {
solve();
}
}
Compilation message
net.cpp:20: warning: ignoring '#pragma GCC Optimize' [-Wunknown-pragmas]
20 | #pragma GCC Optimize("O2")
|
net.cpp: In function 'void setIO(std::string)':
net.cpp:63:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
63 | freopen((s + ".inp").c_str(), "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
64 | freopen((s + ".out").c_str(), "w", stdout);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
3 ms |
14684 KB |
Output is correct |
2 |
Correct |
3 ms |
14684 KB |
Output is correct |
3 |
Correct |
2 ms |
14684 KB |
Output is correct |
4 |
Correct |
3 ms |
14684 KB |
Output is correct |
5 |
Correct |
3 ms |
14684 KB |
Output is correct |
6 |
Correct |
3 ms |
14684 KB |
Output is correct |
7 |
Correct |
3 ms |
14684 KB |
Output is correct |
8 |
Correct |
3 ms |
14684 KB |
Output is correct |
9 |
Correct |
3 ms |
14684 KB |
Output is correct |
10 |
Correct |
3 ms |
14684 KB |
Output is correct |
11 |
Correct |
3 ms |
14684 KB |
Output is correct |
12 |
Correct |
3 ms |
14684 KB |
Output is correct |
13 |
Correct |
3 ms |
14680 KB |
Output is correct |
14 |
Correct |
3 ms |
14684 KB |
Output is correct |
15 |
Correct |
2 ms |
14684 KB |
Output is correct |
16 |
Correct |
3 ms |
14684 KB |
Output is correct |
17 |
Correct |
3 ms |
14684 KB |
Output is correct |
18 |
Correct |
3 ms |
14684 KB |
Output is correct |
19 |
Correct |
3 ms |
14684 KB |
Output is correct |
20 |
Correct |
3 ms |
14680 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
3 ms |
14684 KB |
Output is correct |
2 |
Correct |
3 ms |
14684 KB |
Output is correct |
3 |
Correct |
2 ms |
14684 KB |
Output is correct |
4 |
Correct |
3 ms |
14684 KB |
Output is correct |
5 |
Correct |
3 ms |
14684 KB |
Output is correct |
6 |
Correct |
3 ms |
14684 KB |
Output is correct |
7 |
Correct |
3 ms |
14684 KB |
Output is correct |
8 |
Correct |
3 ms |
14684 KB |
Output is correct |
9 |
Correct |
3 ms |
14684 KB |
Output is correct |
10 |
Correct |
3 ms |
14684 KB |
Output is correct |
11 |
Correct |
3 ms |
14684 KB |
Output is correct |
12 |
Correct |
3 ms |
14684 KB |
Output is correct |
13 |
Correct |
3 ms |
14680 KB |
Output is correct |
14 |
Correct |
3 ms |
14684 KB |
Output is correct |
15 |
Correct |
2 ms |
14684 KB |
Output is correct |
16 |
Correct |
3 ms |
14684 KB |
Output is correct |
17 |
Correct |
3 ms |
14684 KB |
Output is correct |
18 |
Correct |
3 ms |
14684 KB |
Output is correct |
19 |
Correct |
3 ms |
14684 KB |
Output is correct |
20 |
Correct |
3 ms |
14680 KB |
Output is correct |
21 |
Correct |
2 ms |
14680 KB |
Output is correct |
22 |
Correct |
3 ms |
14940 KB |
Output is correct |
23 |
Correct |
3 ms |
14940 KB |
Output is correct |
24 |
Correct |
3 ms |
14940 KB |
Output is correct |
25 |
Correct |
3 ms |
14940 KB |
Output is correct |
26 |
Correct |
3 ms |
14684 KB |
Output is correct |
27 |
Correct |
3 ms |
14940 KB |
Output is correct |
28 |
Correct |
3 ms |
14940 KB |
Output is correct |
29 |
Correct |
3 ms |
14684 KB |
Output is correct |
30 |
Correct |
3 ms |
14680 KB |
Output is correct |
31 |
Correct |
4 ms |
14908 KB |
Output is correct |
32 |
Correct |
3 ms |
14684 KB |
Output is correct |
33 |
Correct |
3 ms |
14684 KB |
Output is correct |
34 |
Correct |
3 ms |
14684 KB |
Output is correct |
35 |
Correct |
3 ms |
14680 KB |
Output is correct |
36 |
Correct |
3 ms |
14684 KB |
Output is correct |
37 |
Correct |
3 ms |
14684 KB |
Output is correct |
38 |
Correct |
3 ms |
14684 KB |
Output is correct |
39 |
Correct |
3 ms |
14684 KB |
Output is correct |
40 |
Correct |
3 ms |
14688 KB |
Output is correct |
41 |
Correct |
3 ms |
14836 KB |
Output is correct |
42 |
Correct |
3 ms |
14688 KB |
Output is correct |
43 |
Correct |
3 ms |
14688 KB |
Output is correct |
44 |
Correct |
4 ms |
14688 KB |
Output is correct |
45 |
Correct |
3 ms |
14880 KB |
Output is correct |
46 |
Correct |
3 ms |
14684 KB |
Output is correct |
47 |
Correct |
3 ms |
14684 KB |
Output is correct |
48 |
Correct |
3 ms |
14684 KB |
Output is correct |
49 |
Correct |
3 ms |
14684 KB |
Output is correct |
50 |
Correct |
2 ms |
14684 KB |
Output is correct |
51 |
Correct |
3 ms |
14684 KB |
Output is correct |
52 |
Correct |
3 ms |
14684 KB |
Output is correct |
53 |
Correct |
3 ms |
14684 KB |
Output is correct |
54 |
Correct |
2 ms |
14684 KB |
Output is correct |
55 |
Correct |
3 ms |
14684 KB |
Output is correct |
56 |
Correct |
3 ms |
14936 KB |
Output is correct |
57 |
Correct |
3 ms |
14684 KB |
Output is correct |
58 |
Correct |
4 ms |
14940 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
3 ms |
14684 KB |
Output is correct |
2 |
Correct |
3 ms |
14684 KB |
Output is correct |
3 |
Correct |
2 ms |
14684 KB |
Output is correct |
4 |
Correct |
3 ms |
14684 KB |
Output is correct |
5 |
Correct |
3 ms |
14684 KB |
Output is correct |
6 |
Correct |
3 ms |
14684 KB |
Output is correct |
7 |
Correct |
3 ms |
14684 KB |
Output is correct |
8 |
Correct |
3 ms |
14684 KB |
Output is correct |
9 |
Correct |
3 ms |
14684 KB |
Output is correct |
10 |
Correct |
3 ms |
14684 KB |
Output is correct |
11 |
Correct |
3 ms |
14684 KB |
Output is correct |
12 |
Correct |
3 ms |
14684 KB |
Output is correct |
13 |
Correct |
3 ms |
14680 KB |
Output is correct |
14 |
Correct |
3 ms |
14684 KB |
Output is correct |
15 |
Correct |
2 ms |
14684 KB |
Output is correct |
16 |
Correct |
3 ms |
14684 KB |
Output is correct |
17 |
Correct |
3 ms |
14684 KB |
Output is correct |
18 |
Correct |
3 ms |
14684 KB |
Output is correct |
19 |
Correct |
3 ms |
14684 KB |
Output is correct |
20 |
Correct |
3 ms |
14680 KB |
Output is correct |
21 |
Correct |
2 ms |
14680 KB |
Output is correct |
22 |
Correct |
3 ms |
14940 KB |
Output is correct |
23 |
Correct |
3 ms |
14940 KB |
Output is correct |
24 |
Correct |
3 ms |
14940 KB |
Output is correct |
25 |
Correct |
3 ms |
14940 KB |
Output is correct |
26 |
Correct |
3 ms |
14684 KB |
Output is correct |
27 |
Correct |
3 ms |
14940 KB |
Output is correct |
28 |
Correct |
3 ms |
14940 KB |
Output is correct |
29 |
Correct |
3 ms |
14684 KB |
Output is correct |
30 |
Correct |
3 ms |
14680 KB |
Output is correct |
31 |
Correct |
4 ms |
14908 KB |
Output is correct |
32 |
Correct |
3 ms |
14684 KB |
Output is correct |
33 |
Correct |
3 ms |
14684 KB |
Output is correct |
34 |
Correct |
3 ms |
14684 KB |
Output is correct |
35 |
Correct |
3 ms |
14680 KB |
Output is correct |
36 |
Correct |
3 ms |
14684 KB |
Output is correct |
37 |
Correct |
3 ms |
14684 KB |
Output is correct |
38 |
Correct |
3 ms |
14684 KB |
Output is correct |
39 |
Correct |
3 ms |
14684 KB |
Output is correct |
40 |
Correct |
3 ms |
14688 KB |
Output is correct |
41 |
Correct |
3 ms |
14836 KB |
Output is correct |
42 |
Correct |
3 ms |
14688 KB |
Output is correct |
43 |
Correct |
3 ms |
14688 KB |
Output is correct |
44 |
Correct |
4 ms |
14688 KB |
Output is correct |
45 |
Correct |
3 ms |
14880 KB |
Output is correct |
46 |
Correct |
3 ms |
14684 KB |
Output is correct |
47 |
Correct |
3 ms |
14684 KB |
Output is correct |
48 |
Correct |
3 ms |
14684 KB |
Output is correct |
49 |
Correct |
3 ms |
14684 KB |
Output is correct |
50 |
Correct |
2 ms |
14684 KB |
Output is correct |
51 |
Correct |
3 ms |
14684 KB |
Output is correct |
52 |
Correct |
3 ms |
14684 KB |
Output is correct |
53 |
Correct |
3 ms |
14684 KB |
Output is correct |
54 |
Correct |
2 ms |
14684 KB |
Output is correct |
55 |
Correct |
3 ms |
14684 KB |
Output is correct |
56 |
Correct |
3 ms |
14936 KB |
Output is correct |
57 |
Correct |
3 ms |
14684 KB |
Output is correct |
58 |
Correct |
4 ms |
14940 KB |
Output is correct |
59 |
Correct |
213 ms |
47296 KB |
Output is correct |
60 |
Correct |
267 ms |
51648 KB |
Output is correct |
61 |
Correct |
3 ms |
14680 KB |
Output is correct |
62 |
Correct |
3 ms |
14684 KB |
Output is correct |
63 |
Correct |
202 ms |
45468 KB |
Output is correct |
64 |
Correct |
4 ms |
15192 KB |
Output is correct |
65 |
Correct |
10 ms |
16728 KB |
Output is correct |
66 |
Correct |
62 ms |
30432 KB |
Output is correct |
67 |
Correct |
338 ms |
49428 KB |
Output is correct |
68 |
Correct |
364 ms |
51656 KB |
Output is correct |
69 |
Correct |
7 ms |
15960 KB |
Output is correct |
70 |
Correct |
54 ms |
27224 KB |
Output is correct |
71 |
Correct |
176 ms |
52412 KB |
Output is correct |
72 |
Correct |
195 ms |
52276 KB |
Output is correct |
73 |
Correct |
57 ms |
23672 KB |
Output is correct |
74 |
Correct |
276 ms |
45836 KB |
Output is correct |
75 |
Correct |
19 ms |
18772 KB |
Output is correct |
76 |
Correct |
217 ms |
51744 KB |
Output is correct |
77 |
Correct |
191 ms |
52060 KB |
Output is correct |
78 |
Correct |
19 ms |
18512 KB |
Output is correct |
79 |
Correct |
335 ms |
47940 KB |
Output is correct |
80 |
Correct |
6 ms |
15196 KB |
Output is correct |
81 |
Correct |
72 ms |
26316 KB |
Output is correct |
82 |
Correct |
219 ms |
52028 KB |
Output is correct |
83 |
Correct |
272 ms |
45928 KB |
Output is correct |
84 |
Correct |
254 ms |
45884 KB |
Output is correct |
85 |
Correct |
325 ms |
45732 KB |
Output is correct |
86 |
Correct |
297 ms |
52516 KB |
Output is correct |
87 |
Correct |
307 ms |
52492 KB |
Output is correct |