1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
| #include<algorithm>
#include<iostream>
#include<iomanip>
#include<cstring>
#include<cstdlib>
#include<vector>
#include<cstdio>
#include<cmath>
#include<queue>
using namespace std;
inline const int Get_Int() {
int num=0,bj=1;
char x=getchar();
while(x<'0'||x>'9') {
if(x=='-')bj=-1;
x=getchar();
}
while(x>='0'&&x<='9') {
num=num*10+x-'0';
x=getchar();
}
return num*bj;
}
const int maxn=200005;
int n,m,Depth[maxn],vst[maxn];
vector<int>edges[maxn];
void AddEdge(int x,int y) {
edges[x].push_back(y);
}
struct Answer {
int a,b,c;
Answer(int _a=0,int _b=0,int _c=0):a(_a),b(_b),c(_c) {}
};
vector<Answer>ans;
int Dfs(int Now,int father,int depth) {
Depth[Now]=depth;
vst[Now]=1;
vector<int>tmp;
for(auto &Next:edges[Now]) {
if(Next==father)continue;
if(vst[Next]) {
if(Depth[Next]<Depth[Now])tmp.push_back(Next);
continue;
}
int extra=Dfs(Next,Now,depth+1);
if(extra!=-1)ans.push_back(Answer(Now,Next,extra));
else tmp.push_back(Next);
}
for(int i=0; i+1<tmp.size(); i+=2)ans.push_back(Answer(tmp[i],Now,tmp[i+1]));
if(tmp.size()&1)return tmp.back();
else return -1;
}
int main() {
int size=40<<20;
__asm__ ("movq %0,%%rsp\n"::"r"((char*)malloc(size)+size));
n=Get_Int();
m=Get_Int();
for(int i=1; i<=m; i++) {
int x=Get_Int(),y=Get_Int();
AddEdge(x,y);
AddEdge(y,x);
}
for(int i=1; i<=n; i++)
if(!vst[i])Dfs(i,0,1);
printf("%d\n",ans.size());
for(auto &i:ans)printf("%d %d %d\n",i.a,i.b,i.c);
exit(0);
}
|
