#include <bits/stdc++.h>
using namespace std;
#define in ({int x=0;int c=getchar(),n=0;for(;!isdigit(c);c=getchar()) n=(c=='-');for(;isdigit(c);c=getchar()) x=x*10+c-'0';n?-x:x;})
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int rnd(int l,int r)
{
return l+rng()%(r-l+1);
}
#define fasty ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define forinc(x,a,b) for(int x=a;x<=b;x++)
#define fordec(x,a,b) for(int x=a;x>=b;x--)
#define forv(a,b) for(auto&a:b)
#define fi first
#define se second
#define pb push_back
#define ii pair<int,int>
#define mt make_tuple
#define all(a) a.begin(),a.end()
#define reset(f,x) memset(f,x,sizeof(f))
#define getbit(x,i) ((x>>i)&1)
#define batbit(x,i) (x|(1ll<<i))
#define tatbit(x,i) (x&~(1<<i))
#define gg exit(0);
const int N = 5e5 + 100;
vector<int> ke[N];
set<int> adj[N];
int n, m;
int num[N], low[N], it, del[N];
stack<int> st;
int cnt;
int id[N], two[N];
void dfs(int u,int p)
{
num[u]=low[u]=++it;
st.push(u);
for(auto v:ke[u])
{
if(del[v]) continue;
if(v==p) continue;
if(!num[v])
{
dfs(v,u);
low[u]=min(low[u],low[v]);
}
else low[u]=min(low[u],num[v]);
}
if(num[u]==low[u])
{
cnt++;
int v;
while(1)
{
v=st.top();
st.pop();
id[v]=cnt;
del[v]=1;
two[cnt] = v;
if(v==u) break;
}
}
}
vector<int> leaf;
void dfs2(int u, int pa)
{
if(adj[u].size() == 1) leaf.pb(two[u]);
for(auto v : adj[u])
{
if(v == pa) continue;
dfs2(v,u);
}
}
main()
{
fasty;
// freopen("bluehouse.inp" , "r" ,stdin);
// freopen("bluehouse.out" , "w", stdout );
// freopen("task.inp" , "r", stdin);
cin >> n;
m=n-1;
forinc(i,1,m)
{
int u,v;
cin >> u >> v;
ke[u].pb(v);
ke[v].pb(u);
}
forinc(i,1,n) if(!num[i]) dfs(i,0);
forinc(i,1,n)
{
for(auto v : ke[i])
{
int x = id[i];
int y = id[v];
if(x!=y)
{
adj[x].insert(y);
adj[y].insert(x);
}
}
}
dfs2(1,0);
int l=0;
int step = leaf.size()/2;
if(leaf.size() % 2 == 0)
{
cout << leaf.size()/2 << "\n";
while(l + leaf.size()/2 < leaf.size())
{
cout << leaf[l] << " " << leaf[l + step] << "\n";
l++;
}
return 0;
}
leaf.pb(leaf[0]);
step++;
cout << leaf.size()/2 << "\n";
while(l + step < leaf.size())
{
cout << leaf[l] << " " << leaf[l + step] << "\n";
l++;
}
}
Compilation message
net.cpp:75:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
75 | main()
| ^~~~
net.cpp: In function 'int main()':
net.cpp:122:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
122 | while(l + step < leaf.size())
| ~~~~~~~~~^~~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
22 ms |
35540 KB |
Output is correct |
2 |
Correct |
18 ms |
35596 KB |
Output is correct |
3 |
Correct |
22 ms |
35592 KB |
Output is correct |
4 |
Correct |
19 ms |
35536 KB |
Output is correct |
5 |
Correct |
22 ms |
35564 KB |
Output is correct |
6 |
Correct |
20 ms |
35540 KB |
Output is correct |
7 |
Correct |
17 ms |
35540 KB |
Output is correct |
8 |
Correct |
19 ms |
35508 KB |
Output is correct |
9 |
Correct |
18 ms |
35496 KB |
Output is correct |
10 |
Correct |
20 ms |
35476 KB |
Output is correct |
11 |
Correct |
21 ms |
35540 KB |
Output is correct |
12 |
Correct |
19 ms |
35516 KB |
Output is correct |
13 |
Correct |
18 ms |
35472 KB |
Output is correct |
14 |
Correct |
20 ms |
35492 KB |
Output is correct |
15 |
Correct |
22 ms |
35532 KB |
Output is correct |
16 |
Correct |
18 ms |
35556 KB |
Output is correct |
17 |
Correct |
19 ms |
35516 KB |
Output is correct |
18 |
Correct |
21 ms |
35540 KB |
Output is correct |
19 |
Correct |
18 ms |
35576 KB |
Output is correct |
20 |
Correct |
19 ms |
35536 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
22 ms |
35540 KB |
Output is correct |
2 |
Correct |
18 ms |
35596 KB |
Output is correct |
3 |
Correct |
22 ms |
35592 KB |
Output is correct |
4 |
Correct |
19 ms |
35536 KB |
Output is correct |
5 |
Correct |
22 ms |
35564 KB |
Output is correct |
6 |
Correct |
20 ms |
35540 KB |
Output is correct |
7 |
Correct |
17 ms |
35540 KB |
Output is correct |
8 |
Correct |
19 ms |
35508 KB |
Output is correct |
9 |
Correct |
18 ms |
35496 KB |
Output is correct |
10 |
Correct |
20 ms |
35476 KB |
Output is correct |
11 |
Correct |
21 ms |
35540 KB |
Output is correct |
12 |
Correct |
19 ms |
35516 KB |
Output is correct |
13 |
Correct |
18 ms |
35472 KB |
Output is correct |
14 |
Correct |
20 ms |
35492 KB |
Output is correct |
15 |
Correct |
22 ms |
35532 KB |
Output is correct |
16 |
Correct |
18 ms |
35556 KB |
Output is correct |
17 |
Correct |
19 ms |
35516 KB |
Output is correct |
18 |
Correct |
21 ms |
35540 KB |
Output is correct |
19 |
Correct |
18 ms |
35576 KB |
Output is correct |
20 |
Correct |
19 ms |
35536 KB |
Output is correct |
21 |
Correct |
23 ms |
35528 KB |
Output is correct |
22 |
Correct |
19 ms |
35796 KB |
Output is correct |
23 |
Correct |
18 ms |
35904 KB |
Output is correct |
24 |
Correct |
19 ms |
35880 KB |
Output is correct |
25 |
Correct |
24 ms |
35880 KB |
Output is correct |
26 |
Correct |
29 ms |
35836 KB |
Output is correct |
27 |
Correct |
21 ms |
35836 KB |
Output is correct |
28 |
Correct |
19 ms |
35796 KB |
Output is correct |
29 |
Correct |
21 ms |
35784 KB |
Output is correct |
30 |
Correct |
24 ms |
35540 KB |
Output is correct |
31 |
Correct |
23 ms |
35884 KB |
Output is correct |
32 |
Correct |
17 ms |
35540 KB |
Output is correct |
33 |
Correct |
20 ms |
35540 KB |
Output is correct |
34 |
Correct |
25 ms |
35540 KB |
Output is correct |
35 |
Correct |
19 ms |
35596 KB |
Output is correct |
36 |
Correct |
22 ms |
35540 KB |
Output is correct |
37 |
Correct |
16 ms |
35668 KB |
Output is correct |
38 |
Correct |
17 ms |
35668 KB |
Output is correct |
39 |
Correct |
16 ms |
35584 KB |
Output is correct |
40 |
Correct |
16 ms |
35576 KB |
Output is correct |
41 |
Correct |
18 ms |
35524 KB |
Output is correct |
42 |
Correct |
18 ms |
35668 KB |
Output is correct |
43 |
Correct |
20 ms |
35668 KB |
Output is correct |
44 |
Correct |
21 ms |
35516 KB |
Output is correct |
45 |
Correct |
20 ms |
35628 KB |
Output is correct |
46 |
Correct |
24 ms |
35668 KB |
Output is correct |
47 |
Correct |
19 ms |
35540 KB |
Output is correct |
48 |
Correct |
20 ms |
35592 KB |
Output is correct |
49 |
Correct |
17 ms |
35732 KB |
Output is correct |
50 |
Correct |
21 ms |
35560 KB |
Output is correct |
51 |
Correct |
17 ms |
35592 KB |
Output is correct |
52 |
Correct |
17 ms |
35668 KB |
Output is correct |
53 |
Correct |
17 ms |
35668 KB |
Output is correct |
54 |
Correct |
20 ms |
35532 KB |
Output is correct |
55 |
Correct |
17 ms |
35592 KB |
Output is correct |
56 |
Correct |
21 ms |
35540 KB |
Output is correct |
57 |
Correct |
17 ms |
35576 KB |
Output is correct |
58 |
Correct |
24 ms |
35836 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
22 ms |
35540 KB |
Output is correct |
2 |
Correct |
18 ms |
35596 KB |
Output is correct |
3 |
Correct |
22 ms |
35592 KB |
Output is correct |
4 |
Correct |
19 ms |
35536 KB |
Output is correct |
5 |
Correct |
22 ms |
35564 KB |
Output is correct |
6 |
Correct |
20 ms |
35540 KB |
Output is correct |
7 |
Correct |
17 ms |
35540 KB |
Output is correct |
8 |
Correct |
19 ms |
35508 KB |
Output is correct |
9 |
Correct |
18 ms |
35496 KB |
Output is correct |
10 |
Correct |
20 ms |
35476 KB |
Output is correct |
11 |
Correct |
21 ms |
35540 KB |
Output is correct |
12 |
Correct |
19 ms |
35516 KB |
Output is correct |
13 |
Correct |
18 ms |
35472 KB |
Output is correct |
14 |
Correct |
20 ms |
35492 KB |
Output is correct |
15 |
Correct |
22 ms |
35532 KB |
Output is correct |
16 |
Correct |
18 ms |
35556 KB |
Output is correct |
17 |
Correct |
19 ms |
35516 KB |
Output is correct |
18 |
Correct |
21 ms |
35540 KB |
Output is correct |
19 |
Correct |
18 ms |
35576 KB |
Output is correct |
20 |
Correct |
19 ms |
35536 KB |
Output is correct |
21 |
Correct |
23 ms |
35528 KB |
Output is correct |
22 |
Correct |
19 ms |
35796 KB |
Output is correct |
23 |
Correct |
18 ms |
35904 KB |
Output is correct |
24 |
Correct |
19 ms |
35880 KB |
Output is correct |
25 |
Correct |
24 ms |
35880 KB |
Output is correct |
26 |
Correct |
29 ms |
35836 KB |
Output is correct |
27 |
Correct |
21 ms |
35836 KB |
Output is correct |
28 |
Correct |
19 ms |
35796 KB |
Output is correct |
29 |
Correct |
21 ms |
35784 KB |
Output is correct |
30 |
Correct |
24 ms |
35540 KB |
Output is correct |
31 |
Correct |
23 ms |
35884 KB |
Output is correct |
32 |
Correct |
17 ms |
35540 KB |
Output is correct |
33 |
Correct |
20 ms |
35540 KB |
Output is correct |
34 |
Correct |
25 ms |
35540 KB |
Output is correct |
35 |
Correct |
19 ms |
35596 KB |
Output is correct |
36 |
Correct |
22 ms |
35540 KB |
Output is correct |
37 |
Correct |
16 ms |
35668 KB |
Output is correct |
38 |
Correct |
17 ms |
35668 KB |
Output is correct |
39 |
Correct |
16 ms |
35584 KB |
Output is correct |
40 |
Correct |
16 ms |
35576 KB |
Output is correct |
41 |
Correct |
18 ms |
35524 KB |
Output is correct |
42 |
Correct |
18 ms |
35668 KB |
Output is correct |
43 |
Correct |
20 ms |
35668 KB |
Output is correct |
44 |
Correct |
21 ms |
35516 KB |
Output is correct |
45 |
Correct |
20 ms |
35628 KB |
Output is correct |
46 |
Correct |
24 ms |
35668 KB |
Output is correct |
47 |
Correct |
19 ms |
35540 KB |
Output is correct |
48 |
Correct |
20 ms |
35592 KB |
Output is correct |
49 |
Correct |
17 ms |
35732 KB |
Output is correct |
50 |
Correct |
21 ms |
35560 KB |
Output is correct |
51 |
Correct |
17 ms |
35592 KB |
Output is correct |
52 |
Correct |
17 ms |
35668 KB |
Output is correct |
53 |
Correct |
17 ms |
35668 KB |
Output is correct |
54 |
Correct |
20 ms |
35532 KB |
Output is correct |
55 |
Correct |
17 ms |
35592 KB |
Output is correct |
56 |
Correct |
21 ms |
35540 KB |
Output is correct |
57 |
Correct |
17 ms |
35576 KB |
Output is correct |
58 |
Correct |
24 ms |
35836 KB |
Output is correct |
59 |
Correct |
780 ms |
110480 KB |
Output is correct |
60 |
Correct |
899 ms |
118964 KB |
Output is correct |
61 |
Correct |
21 ms |
35540 KB |
Output is correct |
62 |
Correct |
20 ms |
35596 KB |
Output is correct |
63 |
Correct |
689 ms |
102460 KB |
Output is correct |
64 |
Correct |
23 ms |
36736 KB |
Output is correct |
65 |
Correct |
32 ms |
40796 KB |
Output is correct |
66 |
Correct |
284 ms |
77200 KB |
Output is correct |
67 |
Correct |
795 ms |
138172 KB |
Output is correct |
68 |
Correct |
791 ms |
136704 KB |
Output is correct |
69 |
Correct |
29 ms |
38220 KB |
Output is correct |
70 |
Correct |
224 ms |
62936 KB |
Output is correct |
71 |
Correct |
853 ms |
122308 KB |
Output is correct |
72 |
Correct |
793 ms |
120888 KB |
Output is correct |
73 |
Correct |
163 ms |
58348 KB |
Output is correct |
74 |
Correct |
746 ms |
117892 KB |
Output is correct |
75 |
Correct |
69 ms |
45032 KB |
Output is correct |
76 |
Correct |
869 ms |
121844 KB |
Output is correct |
77 |
Correct |
842 ms |
122036 KB |
Output is correct |
78 |
Correct |
58 ms |
45612 KB |
Output is correct |
79 |
Correct |
759 ms |
132628 KB |
Output is correct |
80 |
Correct |
21 ms |
36300 KB |
Output is correct |
81 |
Correct |
222 ms |
64096 KB |
Output is correct |
82 |
Correct |
766 ms |
119736 KB |
Output is correct |
83 |
Correct |
757 ms |
117884 KB |
Output is correct |
84 |
Correct |
728 ms |
118008 KB |
Output is correct |
85 |
Correct |
728 ms |
117948 KB |
Output is correct |
86 |
Correct |
775 ms |
119084 KB |
Output is correct |
87 |
Correct |
766 ms |
119088 KB |
Output is correct |