#include<algorithm>
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <cstdio>
#include <vector>
#include <string>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
using namespace std;
#define P(a,b,c) make_pair(a,make_pair(b,c))
#define rep(i,a,n) for (int i=a;i<=n;i++)
#define per(i,a,n) for (int i=n;i>=a;i--)
#define CLR(vis) memset(vis,0,sizeof(vis))
#define MST(vis,pos) memset(vis,pos,sizeof(vis))
#define pb push_back
//#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef pair<int,pair<int,int> >pii;
typedef long long ll;
typedef unsigned long long ull;
const ll mod = 1000000007;
const int INF = 0x3f3f3f3f;
ll gcd(ll a, ll b) {
return b ? gcd(b, a%b) : a;
}
template<class T>inline void gmax(T &A, T B) {
(A<B)&&(A=B);//if(B>A)A=B;
}
template<class T>inline void gmin(T &A, T B) {
(A>B)&&(A=B);//if(B<A)A=B;
}
template <class T>
inline bool scan(T &ret) {
char c;
int sgn;
if(c=getchar(),c==EOF) return 0; //EOF
while(c!='-'&&(c<'0'||c>'9')) c=getchar();
sgn=(c=='-')?-1:1;
ret=(c=='-')?0:(c-'0');
while(c=getchar(),c>='0'&&c<='9') ret=ret*10+(c-'0');
ret*=sgn;
return 1;
}
inline void outt(int x) {
if(x>9) outt(x/10);
putchar(x%10+'0');
}
const int N = 100010,M = 1000010;
int head[N], ver[M], Next[M], tot;
int STA[M], ans[M];
bool vis[M];
int n,m,top,t;
void add(int x,int y){
ver[++tot] = y;
Next[tot] = head[x];
head[x] = tot;
}
void euler(){
STA[++top] = 1;
while(top>0){
int x = STA[top], i = head[x];
while(i && vis[i]) i=Next[i];
if(i){
STA[++top] = ver[i];
vis[i] = vis[i^1] = true;
head[x] = Next[i];
}else{
--top;
ans[++t] = x;
}
}
}
int main(){
cin>>n>>m;
tot = 1;
top = 0;
memset(head, 0 ,sizeof(head));
rep(i,1,m){
int x,y;
scanf("%d%d", &x, &y);
add(x,y), add(y,x);
}
euler();
per(i,1,t){
printf("%d\n", ans[i]);
}
return 0;
}
撰写