#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 5e5 + 2;
const int mod = 1e9 + 7;
vector<int> g[N];
int szl[N];
vector<vector<int>> all;
void Dfs(int s, int e) {
for (int u : g[s]) {
if (u != e) {
Dfs(u, s);
szl[s] += szl[u];
}
}
smax(szl[s], 1);
}
int Dfs1(int s, int e, int t) {
for (int u : g[s]) {
if (u == e) continue;
if (2 * szl[u] > t) return Dfs1(u, s, t);
}
return s;
}
void Dfs2(int s, int e, int r) {
if (g[s].size() == 1) all.back().push_back(s);
for (int u : g[s]) {
if (u == e) continue;
if (s == r) all.push_back({});
Dfs2(u, s, r);
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
for (int i = 0; i < n - 1; i++) {
int u, v; cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
int root = 1;
for (int i = 1; i <= n; i++) if (g[i].size() > g[root].size()) root = i;
Dfs(root, 0);
root = Dfs1(root, 0, szl[root]);
Dfs2(root, 0, root);
int sz = all.size();
priority_queue<pair<int, int>> pq;
vector<array<int, 2>> ans;
for (int i = 0; i < sz; i++) pq.push({all[i].size(), i});
int who = -1;
while (pq.size() > 1) {
int x = pq.top().second; pq.pop();
int y = pq.top().second; pq.pop();
who = all[x].back();
ans.push_back({all[x].back(), all[y].back()});
all[x].pop_back(); all[y].pop_back();
if (all[x].size() > 0) pq.push({all[x].size(), x});
if (all[y].size() > 0) pq.push({all[y].size(), y});
}
if (pq.size() == 1) ans.push_back({who, all[pq.top().second].back()});
cout << ans.size() << en;
for (int i = 0; i < ans.size(); i++) {
cout << ans[i][0] << sp << ans[i][1] << en;
}
return 0;
}
Compilation message
net.cpp: In function 'int main()':
net.cpp:70:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::array<int, 2> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
70 | for (int i = 0; i < ans.size(); i++) {
| ~~^~~~~~~~~~~~
# |
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 |
11992 KB |
Output is correct |
4 |
Correct |
6 ms |
11988 KB |
Output is correct |
5 |
Correct |
6 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
12080 KB |
Output is correct |
7 |
Correct |
6 ms |
11988 KB |
Output is correct |
8 |
Correct |
6 ms |
11988 KB |
Output is correct |
9 |
Correct |
7 ms |
12056 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
7 ms |
11956 KB |
Output is correct |
12 |
Correct |
6 ms |
11988 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
7 ms |
11988 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
12028 KB |
Output is correct |
17 |
Correct |
6 ms |
12068 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
8 ms |
12072 KB |
Output is correct |
20 |
Correct |
6 ms |
12052 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 |
11992 KB |
Output is correct |
4 |
Correct |
6 ms |
11988 KB |
Output is correct |
5 |
Correct |
6 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
12080 KB |
Output is correct |
7 |
Correct |
6 ms |
11988 KB |
Output is correct |
8 |
Correct |
6 ms |
11988 KB |
Output is correct |
9 |
Correct |
7 ms |
12056 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
7 ms |
11956 KB |
Output is correct |
12 |
Correct |
6 ms |
11988 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
7 ms |
11988 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
12028 KB |
Output is correct |
17 |
Correct |
6 ms |
12068 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
8 ms |
12072 KB |
Output is correct |
20 |
Correct |
6 ms |
12052 KB |
Output is correct |
21 |
Correct |
7 ms |
11988 KB |
Output is correct |
22 |
Correct |
7 ms |
12192 KB |
Output is correct |
23 |
Correct |
7 ms |
12340 KB |
Output is correct |
24 |
Correct |
7 ms |
12244 KB |
Output is correct |
25 |
Correct |
7 ms |
12116 KB |
Output is correct |
26 |
Correct |
8 ms |
12116 KB |
Output is correct |
27 |
Correct |
7 ms |
12084 KB |
Output is correct |
28 |
Correct |
7 ms |
12080 KB |
Output is correct |
29 |
Correct |
6 ms |
12116 KB |
Output is correct |
30 |
Correct |
7 ms |
11988 KB |
Output is correct |
31 |
Correct |
9 ms |
12084 KB |
Output is correct |
32 |
Correct |
6 ms |
11988 KB |
Output is correct |
33 |
Correct |
6 ms |
11988 KB |
Output is correct |
34 |
Correct |
7 ms |
12008 KB |
Output is correct |
35 |
Correct |
6 ms |
12020 KB |
Output is correct |
36 |
Correct |
6 ms |
11988 KB |
Output is correct |
37 |
Correct |
6 ms |
12076 KB |
Output is correct |
38 |
Correct |
7 ms |
12092 KB |
Output is correct |
39 |
Correct |
6 ms |
11988 KB |
Output is correct |
40 |
Correct |
6 ms |
11988 KB |
Output is correct |
41 |
Correct |
6 ms |
11988 KB |
Output is correct |
42 |
Correct |
6 ms |
12072 KB |
Output is correct |
43 |
Correct |
7 ms |
12204 KB |
Output is correct |
44 |
Correct |
8 ms |
11988 KB |
Output is correct |
45 |
Correct |
6 ms |
12072 KB |
Output is correct |
46 |
Correct |
6 ms |
12072 KB |
Output is correct |
47 |
Correct |
6 ms |
11988 KB |
Output is correct |
48 |
Correct |
7 ms |
11988 KB |
Output is correct |
49 |
Correct |
7 ms |
12060 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 |
12116 KB |
Output is correct |
54 |
Correct |
6 ms |
12072 KB |
Output is correct |
55 |
Correct |
6 ms |
12076 KB |
Output is correct |
56 |
Correct |
6 ms |
11988 KB |
Output is correct |
57 |
Correct |
7 ms |
12116 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 |
11992 KB |
Output is correct |
4 |
Correct |
6 ms |
11988 KB |
Output is correct |
5 |
Correct |
6 ms |
11988 KB |
Output is correct |
6 |
Correct |
6 ms |
12080 KB |
Output is correct |
7 |
Correct |
6 ms |
11988 KB |
Output is correct |
8 |
Correct |
6 ms |
11988 KB |
Output is correct |
9 |
Correct |
7 ms |
12056 KB |
Output is correct |
10 |
Correct |
6 ms |
11988 KB |
Output is correct |
11 |
Correct |
7 ms |
11956 KB |
Output is correct |
12 |
Correct |
6 ms |
11988 KB |
Output is correct |
13 |
Correct |
6 ms |
11988 KB |
Output is correct |
14 |
Correct |
7 ms |
11988 KB |
Output is correct |
15 |
Correct |
6 ms |
11988 KB |
Output is correct |
16 |
Correct |
6 ms |
12028 KB |
Output is correct |
17 |
Correct |
6 ms |
12068 KB |
Output is correct |
18 |
Correct |
6 ms |
11988 KB |
Output is correct |
19 |
Correct |
8 ms |
12072 KB |
Output is correct |
20 |
Correct |
6 ms |
12052 KB |
Output is correct |
21 |
Correct |
7 ms |
11988 KB |
Output is correct |
22 |
Correct |
7 ms |
12192 KB |
Output is correct |
23 |
Correct |
7 ms |
12340 KB |
Output is correct |
24 |
Correct |
7 ms |
12244 KB |
Output is correct |
25 |
Correct |
7 ms |
12116 KB |
Output is correct |
26 |
Correct |
8 ms |
12116 KB |
Output is correct |
27 |
Correct |
7 ms |
12084 KB |
Output is correct |
28 |
Correct |
7 ms |
12080 KB |
Output is correct |
29 |
Correct |
6 ms |
12116 KB |
Output is correct |
30 |
Correct |
7 ms |
11988 KB |
Output is correct |
31 |
Correct |
9 ms |
12084 KB |
Output is correct |
32 |
Correct |
6 ms |
11988 KB |
Output is correct |
33 |
Correct |
6 ms |
11988 KB |
Output is correct |
34 |
Correct |
7 ms |
12008 KB |
Output is correct |
35 |
Correct |
6 ms |
12020 KB |
Output is correct |
36 |
Correct |
6 ms |
11988 KB |
Output is correct |
37 |
Correct |
6 ms |
12076 KB |
Output is correct |
38 |
Correct |
7 ms |
12092 KB |
Output is correct |
39 |
Correct |
6 ms |
11988 KB |
Output is correct |
40 |
Correct |
6 ms |
11988 KB |
Output is correct |
41 |
Correct |
6 ms |
11988 KB |
Output is correct |
42 |
Correct |
6 ms |
12072 KB |
Output is correct |
43 |
Correct |
7 ms |
12204 KB |
Output is correct |
44 |
Correct |
8 ms |
11988 KB |
Output is correct |
45 |
Correct |
6 ms |
12072 KB |
Output is correct |
46 |
Correct |
6 ms |
12072 KB |
Output is correct |
47 |
Correct |
6 ms |
11988 KB |
Output is correct |
48 |
Correct |
7 ms |
11988 KB |
Output is correct |
49 |
Correct |
7 ms |
12060 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 |
12116 KB |
Output is correct |
54 |
Correct |
6 ms |
12072 KB |
Output is correct |
55 |
Correct |
6 ms |
12076 KB |
Output is correct |
56 |
Correct |
6 ms |
11988 KB |
Output is correct |
57 |
Correct |
7 ms |
12116 KB |
Output is correct |
58 |
Correct |
7 ms |
12116 KB |
Output is correct |
59 |
Correct |
428 ms |
49096 KB |
Output is correct |
60 |
Correct |
420 ms |
42500 KB |
Output is correct |
61 |
Correct |
6 ms |
12072 KB |
Output is correct |
62 |
Correct |
6 ms |
11988 KB |
Output is correct |
63 |
Correct |
342 ms |
43324 KB |
Output is correct |
64 |
Correct |
8 ms |
12500 KB |
Output is correct |
65 |
Correct |
15 ms |
14420 KB |
Output is correct |
66 |
Correct |
144 ms |
31180 KB |
Output is correct |
67 |
Correct |
526 ms |
65576 KB |
Output is correct |
68 |
Correct |
579 ms |
72244 KB |
Output is correct |
69 |
Correct |
14 ms |
13840 KB |
Output is correct |
70 |
Correct |
101 ms |
32036 KB |
Output is correct |
71 |
Correct |
359 ms |
77144 KB |
Output is correct |
72 |
Correct |
389 ms |
72848 KB |
Output is correct |
73 |
Correct |
79 ms |
19932 KB |
Output is correct |
74 |
Correct |
432 ms |
40656 KB |
Output is correct |
75 |
Correct |
31 ms |
17300 KB |
Output is correct |
76 |
Correct |
381 ms |
61444 KB |
Output is correct |
77 |
Correct |
366 ms |
62080 KB |
Output is correct |
78 |
Correct |
32 ms |
16664 KB |
Output is correct |
79 |
Correct |
512 ms |
54588 KB |
Output is correct |
80 |
Correct |
8 ms |
12340 KB |
Output is correct |
81 |
Correct |
110 ms |
27784 KB |
Output is correct |
82 |
Correct |
442 ms |
59520 KB |
Output is correct |
83 |
Correct |
425 ms |
40840 KB |
Output is correct |
84 |
Correct |
420 ms |
41172 KB |
Output is correct |
85 |
Correct |
420 ms |
41156 KB |
Output is correct |
86 |
Correct |
407 ms |
42880 KB |
Output is correct |
87 |
Correct |
396 ms |
42920 KB |
Output is correct |