#include <bits/stdc++.h>
using namespace std;
#include <iostream>
typedef vector<int> vi;
typedef vector<vi> vvi;
#define pb push_back
#define rep(i,a,b) for(int i = a; i < b; i++)
int n;
vvi g;
vi leaf;
int total_leafs;
vvi groups;
vi par;
void dfs(int x, int p) {
par[x] = p;
for (auto y : g[x]) {
if (y == p) continue;
dfs(y, x);
leaf[x] += leaf[y];
}
}
void dfs3(int x, int p) {
par[x] = p;
for (auto y : g[x]) if (y != p) dfs3(y, x);
}
bool test(int r) {
for (auto y : g[r]) if (par[r] != y) if (leaf[y] > total_leafs / 2) return false;
if (total_leafs - leaf[r] > total_leafs / 2) return false;
return true;
}
void dfs2(int x, int p, vi & group) {
for (auto y : g[x]) {
if (y == p) continue;
dfs2(y, x, group);
}
if (g[x].size() == 1) group.pb(x);
}
int main() {
cin >> n;
par.resize(n);
if (n == 2) {
cout << 1 << "\n" << 1 << " " << 2 << endl;
exit(0);
}
g.resize(n);
rep(i,0,n-1) {
int a, b;
cin >> a >> b;
a--;b--;
g[a].pb(b);
g[b].pb(a);
}
leaf.assign(n, 0);
rep(i,0,n) if (g[i].size() == 1) leaf[i] = 1;
int root = 0;
while (leaf[root] > 0) root++;
dfs(root, -1);
total_leafs = leaf[root];
while (!test(root)) root++;
for (auto y : g[root]) {
vi group;
dfs2(y, root, group);
groups.pb(group);
}
priority_queue<pair<int,int>> pq;
int I = 0;
for (auto & gr : groups) {
pq.push({gr.size(), I});
I++;
}
vector<pair<int,int>> ans;
while (true) {
pair<int,int> a = pq.top(); pq.pop();
pair<int,int> b = pq.top(); pq.pop();
if (a.first == 0) break;
if (b.first == 0) {
ans.pb({groups[a.second][0], root});
break;
}
ans.pb({groups[a.second][a.first-1], groups[b.second][b.first-1]});
pq.push({a.first-1, a.second});
pq.push({b.first-1, b.second});
}
cout << ans.size() << endl;
for (auto [a, b] : ans) {
cout << a + 1 << " " << b + 1 << endl;
}
}
Compilation message
net.cpp: In function 'int main()':
net.cpp:106:13: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
106 | for (auto [a, b] : ans) {
| ^
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
0 ms |
212 KB |
Output is correct |
6 |
Correct |
0 ms |
212 KB |
Output is correct |
7 |
Correct |
1 ms |
212 KB |
Output is correct |
8 |
Correct |
0 ms |
212 KB |
Output is correct |
9 |
Correct |
0 ms |
212 KB |
Output is correct |
10 |
Correct |
1 ms |
212 KB |
Output is correct |
11 |
Correct |
0 ms |
212 KB |
Output is correct |
12 |
Correct |
1 ms |
212 KB |
Output is correct |
13 |
Correct |
0 ms |
212 KB |
Output is correct |
14 |
Correct |
0 ms |
212 KB |
Output is correct |
15 |
Correct |
1 ms |
212 KB |
Output is correct |
16 |
Correct |
0 ms |
212 KB |
Output is correct |
17 |
Correct |
0 ms |
212 KB |
Output is correct |
18 |
Correct |
0 ms |
212 KB |
Output is correct |
19 |
Correct |
1 ms |
212 KB |
Output is correct |
20 |
Correct |
1 ms |
212 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
0 ms |
212 KB |
Output is correct |
6 |
Correct |
0 ms |
212 KB |
Output is correct |
7 |
Correct |
1 ms |
212 KB |
Output is correct |
8 |
Correct |
0 ms |
212 KB |
Output is correct |
9 |
Correct |
0 ms |
212 KB |
Output is correct |
10 |
Correct |
1 ms |
212 KB |
Output is correct |
11 |
Correct |
0 ms |
212 KB |
Output is correct |
12 |
Correct |
1 ms |
212 KB |
Output is correct |
13 |
Correct |
0 ms |
212 KB |
Output is correct |
14 |
Correct |
0 ms |
212 KB |
Output is correct |
15 |
Correct |
1 ms |
212 KB |
Output is correct |
16 |
Correct |
0 ms |
212 KB |
Output is correct |
17 |
Correct |
0 ms |
212 KB |
Output is correct |
18 |
Correct |
0 ms |
212 KB |
Output is correct |
19 |
Correct |
1 ms |
212 KB |
Output is correct |
20 |
Correct |
1 ms |
212 KB |
Output is correct |
21 |
Correct |
1 ms |
212 KB |
Output is correct |
22 |
Correct |
3 ms |
468 KB |
Output is correct |
23 |
Correct |
3 ms |
468 KB |
Output is correct |
24 |
Correct |
3 ms |
468 KB |
Output is correct |
25 |
Correct |
2 ms |
468 KB |
Output is correct |
26 |
Correct |
2 ms |
340 KB |
Output is correct |
27 |
Correct |
3 ms |
420 KB |
Output is correct |
28 |
Correct |
2 ms |
340 KB |
Output is correct |
29 |
Correct |
2 ms |
340 KB |
Output is correct |
30 |
Correct |
1 ms |
212 KB |
Output is correct |
31 |
Correct |
3 ms |
468 KB |
Output is correct |
32 |
Correct |
1 ms |
212 KB |
Output is correct |
33 |
Correct |
1 ms |
212 KB |
Output is correct |
34 |
Correct |
1 ms |
296 KB |
Output is correct |
35 |
Correct |
1 ms |
300 KB |
Output is correct |
36 |
Correct |
1 ms |
212 KB |
Output is correct |
37 |
Correct |
1 ms |
340 KB |
Output is correct |
38 |
Correct |
1 ms |
340 KB |
Output is correct |
39 |
Correct |
1 ms |
212 KB |
Output is correct |
40 |
Correct |
1 ms |
212 KB |
Output is correct |
41 |
Correct |
1 ms |
212 KB |
Output is correct |
42 |
Correct |
1 ms |
340 KB |
Output is correct |
43 |
Correct |
3 ms |
432 KB |
Output is correct |
44 |
Correct |
0 ms |
300 KB |
Output is correct |
45 |
Correct |
1 ms |
212 KB |
Output is correct |
46 |
Correct |
2 ms |
340 KB |
Output is correct |
47 |
Correct |
1 ms |
212 KB |
Output is correct |
48 |
Correct |
1 ms |
300 KB |
Output is correct |
49 |
Correct |
2 ms |
312 KB |
Output is correct |
50 |
Correct |
1 ms |
212 KB |
Output is correct |
51 |
Correct |
1 ms |
300 KB |
Output is correct |
52 |
Correct |
1 ms |
212 KB |
Output is correct |
53 |
Correct |
1 ms |
340 KB |
Output is correct |
54 |
Correct |
1 ms |
296 KB |
Output is correct |
55 |
Correct |
1 ms |
340 KB |
Output is correct |
56 |
Correct |
1 ms |
212 KB |
Output is correct |
57 |
Correct |
1 ms |
340 KB |
Output is correct |
58 |
Correct |
3 ms |
468 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
0 ms |
212 KB |
Output is correct |
6 |
Correct |
0 ms |
212 KB |
Output is correct |
7 |
Correct |
1 ms |
212 KB |
Output is correct |
8 |
Correct |
0 ms |
212 KB |
Output is correct |
9 |
Correct |
0 ms |
212 KB |
Output is correct |
10 |
Correct |
1 ms |
212 KB |
Output is correct |
11 |
Correct |
0 ms |
212 KB |
Output is correct |
12 |
Correct |
1 ms |
212 KB |
Output is correct |
13 |
Correct |
0 ms |
212 KB |
Output is correct |
14 |
Correct |
0 ms |
212 KB |
Output is correct |
15 |
Correct |
1 ms |
212 KB |
Output is correct |
16 |
Correct |
0 ms |
212 KB |
Output is correct |
17 |
Correct |
0 ms |
212 KB |
Output is correct |
18 |
Correct |
0 ms |
212 KB |
Output is correct |
19 |
Correct |
1 ms |
212 KB |
Output is correct |
20 |
Correct |
1 ms |
212 KB |
Output is correct |
21 |
Correct |
1 ms |
212 KB |
Output is correct |
22 |
Correct |
3 ms |
468 KB |
Output is correct |
23 |
Correct |
3 ms |
468 KB |
Output is correct |
24 |
Correct |
3 ms |
468 KB |
Output is correct |
25 |
Correct |
2 ms |
468 KB |
Output is correct |
26 |
Correct |
2 ms |
340 KB |
Output is correct |
27 |
Correct |
3 ms |
420 KB |
Output is correct |
28 |
Correct |
2 ms |
340 KB |
Output is correct |
29 |
Correct |
2 ms |
340 KB |
Output is correct |
30 |
Correct |
1 ms |
212 KB |
Output is correct |
31 |
Correct |
3 ms |
468 KB |
Output is correct |
32 |
Correct |
1 ms |
212 KB |
Output is correct |
33 |
Correct |
1 ms |
212 KB |
Output is correct |
34 |
Correct |
1 ms |
296 KB |
Output is correct |
35 |
Correct |
1 ms |
300 KB |
Output is correct |
36 |
Correct |
1 ms |
212 KB |
Output is correct |
37 |
Correct |
1 ms |
340 KB |
Output is correct |
38 |
Correct |
1 ms |
340 KB |
Output is correct |
39 |
Correct |
1 ms |
212 KB |
Output is correct |
40 |
Correct |
1 ms |
212 KB |
Output is correct |
41 |
Correct |
1 ms |
212 KB |
Output is correct |
42 |
Correct |
1 ms |
340 KB |
Output is correct |
43 |
Correct |
3 ms |
432 KB |
Output is correct |
44 |
Correct |
0 ms |
300 KB |
Output is correct |
45 |
Correct |
1 ms |
212 KB |
Output is correct |
46 |
Correct |
2 ms |
340 KB |
Output is correct |
47 |
Correct |
1 ms |
212 KB |
Output is correct |
48 |
Correct |
1 ms |
300 KB |
Output is correct |
49 |
Correct |
2 ms |
312 KB |
Output is correct |
50 |
Correct |
1 ms |
212 KB |
Output is correct |
51 |
Correct |
1 ms |
300 KB |
Output is correct |
52 |
Correct |
1 ms |
212 KB |
Output is correct |
53 |
Correct |
1 ms |
340 KB |
Output is correct |
54 |
Correct |
1 ms |
296 KB |
Output is correct |
55 |
Correct |
1 ms |
340 KB |
Output is correct |
56 |
Correct |
1 ms |
212 KB |
Output is correct |
57 |
Correct |
1 ms |
340 KB |
Output is correct |
58 |
Correct |
3 ms |
468 KB |
Output is correct |
59 |
Correct |
762 ms |
44212 KB |
Output is correct |
60 |
Correct |
944 ms |
38060 KB |
Output is correct |
61 |
Correct |
1 ms |
212 KB |
Output is correct |
62 |
Correct |
1 ms |
212 KB |
Output is correct |
63 |
Correct |
713 ms |
37648 KB |
Output is correct |
64 |
Correct |
5 ms |
852 KB |
Output is correct |
65 |
Correct |
20 ms |
3056 KB |
Output is correct |
66 |
Correct |
224 ms |
22420 KB |
Output is correct |
67 |
Correct |
734 ms |
49080 KB |
Output is correct |
68 |
Correct |
748 ms |
50024 KB |
Output is correct |
69 |
Correct |
21 ms |
2544 KB |
Output is correct |
70 |
Correct |
263 ms |
22820 KB |
Output is correct |
71 |
Correct |
878 ms |
72916 KB |
Output is correct |
72 |
Correct |
840 ms |
69144 KB |
Output is correct |
73 |
Correct |
199 ms |
10508 KB |
Output is correct |
74 |
Correct |
802 ms |
37484 KB |
Output is correct |
75 |
Correct |
83 ms |
6672 KB |
Output is correct |
76 |
Correct |
832 ms |
57156 KB |
Output is correct |
77 |
Correct |
833 ms |
58276 KB |
Output is correct |
78 |
Correct |
53 ms |
5428 KB |
Output is correct |
79 |
Correct |
720 ms |
46620 KB |
Output is correct |
80 |
Correct |
7 ms |
724 KB |
Output is correct |
81 |
Correct |
250 ms |
18852 KB |
Output is correct |
82 |
Correct |
824 ms |
54988 KB |
Output is correct |
83 |
Correct |
756 ms |
35936 KB |
Output is correct |
84 |
Correct |
807 ms |
36012 KB |
Output is correct |
85 |
Correct |
779 ms |
35888 KB |
Output is correct |
86 |
Correct |
779 ms |
37396 KB |
Output is correct |
87 |
Correct |
825 ms |
37508 KB |
Output is correct |