#include <bits/stdc++.h>
using namespace std;
const int N = 500*1000+5;
vector<int> g[N];
bool used[N];
int timer, tin[N], fup[N];
bool f = false;
void dfs (int v, int p = -1) {
used[v] = true;
tin[v] = fup[v] = timer++;
for (size_t i=0; i<g[v].size(); ++i) {
int to = g[v][i];
if (to == p) continue;
if (used[to])
fup[v] = min (fup[v], tin[to]);
else {
dfs (to, v);
fup[v] = min (fup[v], fup[to]);
if (fup[to] > tin[v])
f = true;
}
}
}
int n;
void find_bridges() {
timer = 0;
f = false;
memset(tin,0,sizeof(tin));
memset(fup,0,sizeof(fup));
for (int i=1; i<=n; ++i)
used[i] = false;
for (int i=1; i<=n; ++i)
if (!used[i])
dfs (i);
}
int main(){
ios_base::sync_with_stdio(false);
cin>>n;
for(int i = 1;i<=n-1;i++){
int x,y;
cin>>x>>y;
g[x].push_back(y);
g[y].push_back(x);
}
vector<int> lf;
for(int i = 1;i<=n;i++){
if(g[i].size() == 1) lf.push_back(i);
}
/*
cout<<(lf.size()+1)/2<<endl;
for(int i = 0;i<lf.size()-1;i+=2){
cout<<lf[i]<< " "<<lf[i+1]<<endl;
}
if(lf.size()%2){
cout<<lf[lf.size()-1]<<" "<<lf[lf.size()-2]<<endl;
}*/
int tim = 50;
while(tim--){
random_shuffle(lf.begin(),lf.end());
//cout<<(lf.size()+1)/2<<endl;
for(int i = 0;i<lf.size()-1;i+=2){
//cout<<lf[i]<< " "<<lf[i+1]<<endl;
g[lf[i]].push_back(lf[i+1]);
g[lf[i+1]].push_back(lf[i]);
}
if(lf.size()%2){
// cout<<lf[lf.size()-1]<<" "<<lf[lf.size()-2]<<endl;
g[lf[lf.size()-1]].push_back(lf[lf.size()-2]);
g[lf[lf.size()-2]].push_back(lf[lf.size()-1]);
}
find_bridges();
if(!f){
cout<<(lf.size()+1)/2<<endl;
for(int i = 0;i<lf.size()-1;i+=2){
cout<<lf[i]<< " "<<lf[i+1]<<endl;
}
if(lf.size()%2){
cout<<lf[lf.size()-1]<<" "<<lf[lf.size()-2]<<endl;
}
return 0;
}
for(int i = 0;i<lf.size()-1;i+=2){
//cout<<lf[i]<< " "<<lf[i+1]<<endl;
g[lf[i]].pop_back();
g[lf[i+1]].pop_back();
}
if(lf.size()%2){
// cout<<lf[lf.size()-1]<<" "<<lf[lf.size()-2]<<endl;
g[lf[lf.size()-1]].pop_back();
g[lf[lf.size()-2]].pop_back();
}
}
return 0;
}
Compilation message
net.cpp: In function 'int main()':
net.cpp:61:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 0;i<lf.size()-1;i+=2){
~^~~~~~~~~~~~
net.cpp:74:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 0;i<lf.size()-1;i+=2){
~^~~~~~~~~~~~
net.cpp:82:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 0;i<lf.size()-1;i+=2){
~^~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
20 ms |
16012 KB |
Output is correct |
2 |
Correct |
21 ms |
15992 KB |
Output is correct |
3 |
Correct |
18 ms |
15992 KB |
Output is correct |
4 |
Correct |
16 ms |
15992 KB |
Output is correct |
5 |
Correct |
16 ms |
15992 KB |
Output is correct |
6 |
Correct |
16 ms |
15992 KB |
Output is correct |
7 |
Correct |
16 ms |
15992 KB |
Output is correct |
8 |
Correct |
16 ms |
15992 KB |
Output is correct |
9 |
Correct |
17 ms |
16040 KB |
Output is correct |
10 |
Correct |
16 ms |
16020 KB |
Output is correct |
11 |
Correct |
16 ms |
16028 KB |
Output is correct |
12 |
Correct |
16 ms |
15992 KB |
Output is correct |
13 |
Correct |
19 ms |
16068 KB |
Output is correct |
14 |
Correct |
17 ms |
15992 KB |
Output is correct |
15 |
Correct |
17 ms |
15992 KB |
Output is correct |
16 |
Correct |
16 ms |
15992 KB |
Output is correct |
17 |
Correct |
17 ms |
15992 KB |
Output is correct |
18 |
Correct |
16 ms |
15992 KB |
Output is correct |
19 |
Correct |
16 ms |
15992 KB |
Output is correct |
20 |
Correct |
16 ms |
15992 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
20 ms |
16012 KB |
Output is correct |
2 |
Correct |
21 ms |
15992 KB |
Output is correct |
3 |
Correct |
18 ms |
15992 KB |
Output is correct |
4 |
Correct |
16 ms |
15992 KB |
Output is correct |
5 |
Correct |
16 ms |
15992 KB |
Output is correct |
6 |
Correct |
16 ms |
15992 KB |
Output is correct |
7 |
Correct |
16 ms |
15992 KB |
Output is correct |
8 |
Correct |
16 ms |
15992 KB |
Output is correct |
9 |
Correct |
17 ms |
16040 KB |
Output is correct |
10 |
Correct |
16 ms |
16020 KB |
Output is correct |
11 |
Correct |
16 ms |
16028 KB |
Output is correct |
12 |
Correct |
16 ms |
15992 KB |
Output is correct |
13 |
Correct |
19 ms |
16068 KB |
Output is correct |
14 |
Correct |
17 ms |
15992 KB |
Output is correct |
15 |
Correct |
17 ms |
15992 KB |
Output is correct |
16 |
Correct |
16 ms |
15992 KB |
Output is correct |
17 |
Correct |
17 ms |
15992 KB |
Output is correct |
18 |
Correct |
16 ms |
15992 KB |
Output is correct |
19 |
Correct |
16 ms |
15992 KB |
Output is correct |
20 |
Correct |
16 ms |
15992 KB |
Output is correct |
21 |
Correct |
19 ms |
15992 KB |
Output is correct |
22 |
Correct |
20 ms |
16120 KB |
Output is correct |
23 |
Correct |
23 ms |
16092 KB |
Output is correct |
24 |
Correct |
20 ms |
16120 KB |
Output is correct |
25 |
Correct |
19 ms |
16148 KB |
Output is correct |
26 |
Correct |
19 ms |
16120 KB |
Output is correct |
27 |
Correct |
19 ms |
16120 KB |
Output is correct |
28 |
Correct |
19 ms |
16120 KB |
Output is correct |
29 |
Correct |
18 ms |
16248 KB |
Output is correct |
30 |
Correct |
17 ms |
15992 KB |
Output is correct |
31 |
Correct |
19 ms |
16124 KB |
Output is correct |
32 |
Correct |
16 ms |
15992 KB |
Output is correct |
33 |
Correct |
19 ms |
15992 KB |
Output is correct |
34 |
Correct |
16 ms |
15992 KB |
Output is correct |
35 |
Correct |
16 ms |
15992 KB |
Output is correct |
36 |
Correct |
16 ms |
16020 KB |
Output is correct |
37 |
Correct |
16 ms |
15992 KB |
Output is correct |
38 |
Correct |
16 ms |
15992 KB |
Output is correct |
39 |
Correct |
16 ms |
15992 KB |
Output is correct |
40 |
Correct |
16 ms |
15992 KB |
Output is correct |
41 |
Correct |
16 ms |
16120 KB |
Output is correct |
42 |
Correct |
16 ms |
15992 KB |
Output is correct |
43 |
Correct |
18 ms |
16120 KB |
Output is correct |
44 |
Correct |
16 ms |
16120 KB |
Output is correct |
45 |
Correct |
16 ms |
15992 KB |
Output is correct |
46 |
Correct |
17 ms |
16120 KB |
Output is correct |
47 |
Correct |
16 ms |
15996 KB |
Output is correct |
48 |
Correct |
16 ms |
15992 KB |
Output is correct |
49 |
Correct |
18 ms |
16120 KB |
Output is correct |
50 |
Correct |
16 ms |
15992 KB |
Output is correct |
51 |
Correct |
16 ms |
15992 KB |
Output is correct |
52 |
Correct |
16 ms |
16040 KB |
Output is correct |
53 |
Correct |
17 ms |
16024 KB |
Output is correct |
54 |
Correct |
16 ms |
15996 KB |
Output is correct |
55 |
Correct |
16 ms |
15992 KB |
Output is correct |
56 |
Correct |
16 ms |
15992 KB |
Output is correct |
57 |
Correct |
17 ms |
15992 KB |
Output is correct |
58 |
Correct |
19 ms |
16120 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
20 ms |
16012 KB |
Output is correct |
2 |
Correct |
21 ms |
15992 KB |
Output is correct |
3 |
Correct |
18 ms |
15992 KB |
Output is correct |
4 |
Correct |
16 ms |
15992 KB |
Output is correct |
5 |
Correct |
16 ms |
15992 KB |
Output is correct |
6 |
Correct |
16 ms |
15992 KB |
Output is correct |
7 |
Correct |
16 ms |
15992 KB |
Output is correct |
8 |
Correct |
16 ms |
15992 KB |
Output is correct |
9 |
Correct |
17 ms |
16040 KB |
Output is correct |
10 |
Correct |
16 ms |
16020 KB |
Output is correct |
11 |
Correct |
16 ms |
16028 KB |
Output is correct |
12 |
Correct |
16 ms |
15992 KB |
Output is correct |
13 |
Correct |
19 ms |
16068 KB |
Output is correct |
14 |
Correct |
17 ms |
15992 KB |
Output is correct |
15 |
Correct |
17 ms |
15992 KB |
Output is correct |
16 |
Correct |
16 ms |
15992 KB |
Output is correct |
17 |
Correct |
17 ms |
15992 KB |
Output is correct |
18 |
Correct |
16 ms |
15992 KB |
Output is correct |
19 |
Correct |
16 ms |
15992 KB |
Output is correct |
20 |
Correct |
16 ms |
15992 KB |
Output is correct |
21 |
Correct |
19 ms |
15992 KB |
Output is correct |
22 |
Correct |
20 ms |
16120 KB |
Output is correct |
23 |
Correct |
23 ms |
16092 KB |
Output is correct |
24 |
Correct |
20 ms |
16120 KB |
Output is correct |
25 |
Correct |
19 ms |
16148 KB |
Output is correct |
26 |
Correct |
19 ms |
16120 KB |
Output is correct |
27 |
Correct |
19 ms |
16120 KB |
Output is correct |
28 |
Correct |
19 ms |
16120 KB |
Output is correct |
29 |
Correct |
18 ms |
16248 KB |
Output is correct |
30 |
Correct |
17 ms |
15992 KB |
Output is correct |
31 |
Correct |
19 ms |
16124 KB |
Output is correct |
32 |
Correct |
16 ms |
15992 KB |
Output is correct |
33 |
Correct |
19 ms |
15992 KB |
Output is correct |
34 |
Correct |
16 ms |
15992 KB |
Output is correct |
35 |
Correct |
16 ms |
15992 KB |
Output is correct |
36 |
Correct |
16 ms |
16020 KB |
Output is correct |
37 |
Correct |
16 ms |
15992 KB |
Output is correct |
38 |
Correct |
16 ms |
15992 KB |
Output is correct |
39 |
Correct |
16 ms |
15992 KB |
Output is correct |
40 |
Correct |
16 ms |
15992 KB |
Output is correct |
41 |
Correct |
16 ms |
16120 KB |
Output is correct |
42 |
Correct |
16 ms |
15992 KB |
Output is correct |
43 |
Correct |
18 ms |
16120 KB |
Output is correct |
44 |
Correct |
16 ms |
16120 KB |
Output is correct |
45 |
Correct |
16 ms |
15992 KB |
Output is correct |
46 |
Correct |
17 ms |
16120 KB |
Output is correct |
47 |
Correct |
16 ms |
15996 KB |
Output is correct |
48 |
Correct |
16 ms |
15992 KB |
Output is correct |
49 |
Correct |
18 ms |
16120 KB |
Output is correct |
50 |
Correct |
16 ms |
15992 KB |
Output is correct |
51 |
Correct |
16 ms |
15992 KB |
Output is correct |
52 |
Correct |
16 ms |
16040 KB |
Output is correct |
53 |
Correct |
17 ms |
16024 KB |
Output is correct |
54 |
Correct |
16 ms |
15996 KB |
Output is correct |
55 |
Correct |
16 ms |
15992 KB |
Output is correct |
56 |
Correct |
16 ms |
15992 KB |
Output is correct |
57 |
Correct |
17 ms |
15992 KB |
Output is correct |
58 |
Correct |
19 ms |
16120 KB |
Output is correct |
59 |
Correct |
1014 ms |
55456 KB |
Output is correct |
60 |
Correct |
1167 ms |
58748 KB |
Output is correct |
61 |
Correct |
16 ms |
15992 KB |
Output is correct |
62 |
Correct |
19 ms |
15992 KB |
Output is correct |
63 |
Correct |
1006 ms |
52276 KB |
Output is correct |
64 |
Correct |
18 ms |
16376 KB |
Output is correct |
65 |
Correct |
32 ms |
17912 KB |
Output is correct |
66 |
Correct |
183 ms |
29792 KB |
Output is correct |
67 |
Correct |
624 ms |
70272 KB |
Output is correct |
68 |
Correct |
662 ms |
55408 KB |
Output is correct |
69 |
Correct |
45 ms |
16888 KB |
Output is correct |
70 |
Correct |
337 ms |
25448 KB |
Output is correct |
71 |
Correct |
1223 ms |
46620 KB |
Output is correct |
72 |
Correct |
1169 ms |
45240 KB |
Output is correct |
73 |
Correct |
253 ms |
27172 KB |
Output is correct |
74 |
Correct |
1039 ms |
56228 KB |
Output is correct |
75 |
Correct |
122 ms |
19320 KB |
Output is correct |
76 |
Correct |
1219 ms |
46048 KB |
Output is correct |
77 |
Correct |
1241 ms |
46260 KB |
Output is correct |
78 |
Correct |
68 ms |
20472 KB |
Output is correct |
79 |
Correct |
608 ms |
63552 KB |
Output is correct |
80 |
Correct |
23 ms |
16248 KB |
Output is correct |
81 |
Correct |
351 ms |
26608 KB |
Output is correct |
82 |
Correct |
1119 ms |
47252 KB |
Output is correct |
83 |
Correct |
1022 ms |
56428 KB |
Output is correct |
84 |
Correct |
1006 ms |
56400 KB |
Output is correct |
85 |
Correct |
1046 ms |
56348 KB |
Output is correct |
86 |
Correct |
1161 ms |
58680 KB |
Output is correct |
87 |
Correct |
1163 ms |
58660 KB |
Output is correct |