// In the name of God
// We are everywhere while we are nowhere(Haj NEZAM...)
#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define lc 2 * v
#define rc 2 * v + 1
#define PB push_back
#define MP make_pair
#define ll long long
#define int long long
#define ld long double
#define mid (s + e) / 2
#define pii pair <int , int>
#define _sz(e) (int)e.size()
#define _all(e) e.begin() , e.end()
#define pll pair <long long , long long>
#define piii pair <int , pair <int , int> >
#define FAST ios::sync_with_stdio(0);cin.tie(0)
#define UNI(e) e.resize(unique(_all(e)) - e.begin())
#define kill(e) cout << e << '\n'
#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
const int maxn = 5e5 + 5 , N = 1e6 + 5 , SQ = 450 , base = 800287 , mod = 1e9 + 7 , INF = 1e9 + 5 , lg = 20;
const ld eps = 1e-4;
int n , root;
vector <int> vec;
vector <int> edges[maxn];
void dfs(int v , int p = -1) {
if(_sz(edges[v]) == 1) {
vec.PB(v);
}
for (auto u : edges[v]) {
if(u != p) {
dfs(u , v);
}
}
}
int32_t main() {
FAST;
cin >> n;
for (int i = 0; i < n - 1; ++i) {
int x , y; cin >> x >> y;
x-- , y--;
edges[x].PB(y);
edges[y].PB(x);
}
for (int i = 0; i < n; ++i) {
if(_sz(edges[i]) > 1) {root = i;}
}
dfs(root);
int ans = (_sz(vec) + 1) / 2;
cout << ans << '\n';
for (int i = 0; i < ans; ++i) {
int nxt = min(_sz(vec) - 1 , i + ans);
cout << vec[i] + 1 << ' ' << vec[nxt] + 1 << '\n';
}
}
// Mistakes:
// * Read the problem carefully.
// * Check maxn.
// * Overflows.
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
7 ms |
11980 KB |
Output is correct |
2 |
Correct |
7 ms |
12056 KB |
Output is correct |
3 |
Correct |
6 ms |
11980 KB |
Output is correct |
4 |
Correct |
7 ms |
11980 KB |
Output is correct |
5 |
Correct |
6 ms |
11980 KB |
Output is correct |
6 |
Correct |
7 ms |
11980 KB |
Output is correct |
7 |
Correct |
7 ms |
11980 KB |
Output is correct |
8 |
Correct |
8 ms |
11984 KB |
Output is correct |
9 |
Correct |
7 ms |
11980 KB |
Output is correct |
10 |
Correct |
8 ms |
11980 KB |
Output is correct |
11 |
Correct |
6 ms |
11980 KB |
Output is correct |
12 |
Correct |
7 ms |
11980 KB |
Output is correct |
13 |
Correct |
7 ms |
11980 KB |
Output is correct |
14 |
Correct |
7 ms |
11996 KB |
Output is correct |
15 |
Correct |
7 ms |
11980 KB |
Output is correct |
16 |
Correct |
7 ms |
11980 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 |
11980 KB |
Output is correct |
20 |
Correct |
7 ms |
11980 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
7 ms |
11980 KB |
Output is correct |
2 |
Correct |
7 ms |
12056 KB |
Output is correct |
3 |
Correct |
6 ms |
11980 KB |
Output is correct |
4 |
Correct |
7 ms |
11980 KB |
Output is correct |
5 |
Correct |
6 ms |
11980 KB |
Output is correct |
6 |
Correct |
7 ms |
11980 KB |
Output is correct |
7 |
Correct |
7 ms |
11980 KB |
Output is correct |
8 |
Correct |
8 ms |
11984 KB |
Output is correct |
9 |
Correct |
7 ms |
11980 KB |
Output is correct |
10 |
Correct |
8 ms |
11980 KB |
Output is correct |
11 |
Correct |
6 ms |
11980 KB |
Output is correct |
12 |
Correct |
7 ms |
11980 KB |
Output is correct |
13 |
Correct |
7 ms |
11980 KB |
Output is correct |
14 |
Correct |
7 ms |
11996 KB |
Output is correct |
15 |
Correct |
7 ms |
11980 KB |
Output is correct |
16 |
Correct |
7 ms |
11980 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 |
11980 KB |
Output is correct |
20 |
Correct |
7 ms |
11980 KB |
Output is correct |
21 |
Correct |
7 ms |
11984 KB |
Output is correct |
22 |
Correct |
8 ms |
12108 KB |
Output is correct |
23 |
Correct |
9 ms |
12108 KB |
Output is correct |
24 |
Correct |
8 ms |
12096 KB |
Output is correct |
25 |
Correct |
7 ms |
12100 KB |
Output is correct |
26 |
Correct |
7 ms |
12112 KB |
Output is correct |
27 |
Correct |
8 ms |
12108 KB |
Output is correct |
28 |
Correct |
8 ms |
12108 KB |
Output is correct |
29 |
Correct |
8 ms |
12108 KB |
Output is correct |
30 |
Correct |
7 ms |
11980 KB |
Output is correct |
31 |
Correct |
8 ms |
12108 KB |
Output is correct |
32 |
Correct |
7 ms |
12044 KB |
Output is correct |
33 |
Correct |
7 ms |
11980 KB |
Output is correct |
34 |
Correct |
7 ms |
11984 KB |
Output is correct |
35 |
Correct |
8 ms |
11980 KB |
Output is correct |
36 |
Correct |
7 ms |
11984 KB |
Output is correct |
37 |
Correct |
8 ms |
11980 KB |
Output is correct |
38 |
Correct |
8 ms |
12108 KB |
Output is correct |
39 |
Correct |
7 ms |
11980 KB |
Output is correct |
40 |
Correct |
7 ms |
11980 KB |
Output is correct |
41 |
Correct |
7 ms |
11980 KB |
Output is correct |
42 |
Correct |
7 ms |
11980 KB |
Output is correct |
43 |
Correct |
8 ms |
12108 KB |
Output is correct |
44 |
Correct |
7 ms |
11980 KB |
Output is correct |
45 |
Correct |
7 ms |
11992 KB |
Output is correct |
46 |
Correct |
7 ms |
11980 KB |
Output is correct |
47 |
Correct |
7 ms |
11980 KB |
Output is correct |
48 |
Correct |
8 ms |
12072 KB |
Output is correct |
49 |
Correct |
7 ms |
12108 KB |
Output is correct |
50 |
Correct |
7 ms |
11980 KB |
Output is correct |
51 |
Correct |
7 ms |
11980 KB |
Output is correct |
52 |
Correct |
7 ms |
11980 KB |
Output is correct |
53 |
Correct |
7 ms |
12080 KB |
Output is correct |
54 |
Correct |
7 ms |
11980 KB |
Output is correct |
55 |
Correct |
7 ms |
11980 KB |
Output is correct |
56 |
Correct |
8 ms |
11980 KB |
Output is correct |
57 |
Correct |
7 ms |
11980 KB |
Output is correct |
58 |
Correct |
10 ms |
12108 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
7 ms |
11980 KB |
Output is correct |
2 |
Correct |
7 ms |
12056 KB |
Output is correct |
3 |
Correct |
6 ms |
11980 KB |
Output is correct |
4 |
Correct |
7 ms |
11980 KB |
Output is correct |
5 |
Correct |
6 ms |
11980 KB |
Output is correct |
6 |
Correct |
7 ms |
11980 KB |
Output is correct |
7 |
Correct |
7 ms |
11980 KB |
Output is correct |
8 |
Correct |
8 ms |
11984 KB |
Output is correct |
9 |
Correct |
7 ms |
11980 KB |
Output is correct |
10 |
Correct |
8 ms |
11980 KB |
Output is correct |
11 |
Correct |
6 ms |
11980 KB |
Output is correct |
12 |
Correct |
7 ms |
11980 KB |
Output is correct |
13 |
Correct |
7 ms |
11980 KB |
Output is correct |
14 |
Correct |
7 ms |
11996 KB |
Output is correct |
15 |
Correct |
7 ms |
11980 KB |
Output is correct |
16 |
Correct |
7 ms |
11980 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 |
11980 KB |
Output is correct |
20 |
Correct |
7 ms |
11980 KB |
Output is correct |
21 |
Correct |
7 ms |
11984 KB |
Output is correct |
22 |
Correct |
8 ms |
12108 KB |
Output is correct |
23 |
Correct |
9 ms |
12108 KB |
Output is correct |
24 |
Correct |
8 ms |
12096 KB |
Output is correct |
25 |
Correct |
7 ms |
12100 KB |
Output is correct |
26 |
Correct |
7 ms |
12112 KB |
Output is correct |
27 |
Correct |
8 ms |
12108 KB |
Output is correct |
28 |
Correct |
8 ms |
12108 KB |
Output is correct |
29 |
Correct |
8 ms |
12108 KB |
Output is correct |
30 |
Correct |
7 ms |
11980 KB |
Output is correct |
31 |
Correct |
8 ms |
12108 KB |
Output is correct |
32 |
Correct |
7 ms |
12044 KB |
Output is correct |
33 |
Correct |
7 ms |
11980 KB |
Output is correct |
34 |
Correct |
7 ms |
11984 KB |
Output is correct |
35 |
Correct |
8 ms |
11980 KB |
Output is correct |
36 |
Correct |
7 ms |
11984 KB |
Output is correct |
37 |
Correct |
8 ms |
11980 KB |
Output is correct |
38 |
Correct |
8 ms |
12108 KB |
Output is correct |
39 |
Correct |
7 ms |
11980 KB |
Output is correct |
40 |
Correct |
7 ms |
11980 KB |
Output is correct |
41 |
Correct |
7 ms |
11980 KB |
Output is correct |
42 |
Correct |
7 ms |
11980 KB |
Output is correct |
43 |
Correct |
8 ms |
12108 KB |
Output is correct |
44 |
Correct |
7 ms |
11980 KB |
Output is correct |
45 |
Correct |
7 ms |
11992 KB |
Output is correct |
46 |
Correct |
7 ms |
11980 KB |
Output is correct |
47 |
Correct |
7 ms |
11980 KB |
Output is correct |
48 |
Correct |
8 ms |
12072 KB |
Output is correct |
49 |
Correct |
7 ms |
12108 KB |
Output is correct |
50 |
Correct |
7 ms |
11980 KB |
Output is correct |
51 |
Correct |
7 ms |
11980 KB |
Output is correct |
52 |
Correct |
7 ms |
11980 KB |
Output is correct |
53 |
Correct |
7 ms |
12080 KB |
Output is correct |
54 |
Correct |
7 ms |
11980 KB |
Output is correct |
55 |
Correct |
7 ms |
11980 KB |
Output is correct |
56 |
Correct |
8 ms |
11980 KB |
Output is correct |
57 |
Correct |
7 ms |
11980 KB |
Output is correct |
58 |
Correct |
10 ms |
12108 KB |
Output is correct |
59 |
Correct |
409 ms |
34524 KB |
Output is correct |
60 |
Correct |
416 ms |
36780 KB |
Output is correct |
61 |
Correct |
7 ms |
11980 KB |
Output is correct |
62 |
Correct |
7 ms |
11980 KB |
Output is correct |
63 |
Correct |
327 ms |
31512 KB |
Output is correct |
64 |
Correct |
9 ms |
12428 KB |
Output is correct |
65 |
Correct |
17 ms |
13688 KB |
Output is correct |
66 |
Correct |
172 ms |
24556 KB |
Output is correct |
67 |
Correct |
531 ms |
58824 KB |
Output is correct |
68 |
Correct |
523 ms |
50060 KB |
Output is correct |
69 |
Correct |
15 ms |
12876 KB |
Output is correct |
70 |
Correct |
112 ms |
21148 KB |
Output is correct |
71 |
Correct |
324 ms |
39020 KB |
Output is correct |
72 |
Correct |
348 ms |
37984 KB |
Output is correct |
73 |
Correct |
98 ms |
18324 KB |
Output is correct |
74 |
Correct |
480 ms |
34440 KB |
Output is correct |
75 |
Correct |
30 ms |
15064 KB |
Output is correct |
76 |
Correct |
366 ms |
38552 KB |
Output is correct |
77 |
Correct |
322 ms |
39072 KB |
Output is correct |
78 |
Correct |
35 ms |
15364 KB |
Output is correct |
79 |
Correct |
519 ms |
42016 KB |
Output is correct |
80 |
Correct |
9 ms |
12236 KB |
Output is correct |
81 |
Correct |
121 ms |
20584 KB |
Output is correct |
82 |
Correct |
405 ms |
36784 KB |
Output is correct |
83 |
Correct |
523 ms |
34436 KB |
Output is correct |
84 |
Correct |
485 ms |
34488 KB |
Output is correct |
85 |
Correct |
514 ms |
34464 KB |
Output is correct |
86 |
Correct |
455 ms |
36784 KB |
Output is correct |
87 |
Correct |
507 ms |
36740 KB |
Output is correct |