http://poj.org/problem?id=2230

C++版本一

参考文章：https://blog.csdn.net/weixin_43272781/article/details/88553573

题解：vector 存边+欧拉回路

/*
*@Author:   STZG
*@Language: C++
*/
//#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
int ans,cnt,flag,temp,sum;
int vis[N];
char str;
struct node{
    int id,v;
}x;
vector<node> G[N];
void dfs(int u){
    for(int i=0,j=G[u].size();i<j;i++){
        node tmp=G[u][i];
        if(vis[tmp.id])
            continue;
        vis[tmp.id]=1;
        dfs(tmp.v);
    }
    printf("%d\n",u);
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    //while(t--){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++){
        scanf("%d%d",&u,&v);
        x.v=v;
        x.id=2*i-1;
        G[u].push_back(x);
        x.v=u;
        x.id=2*i;
        G[v].push_back(x);
    }
    dfs(1);
    //}

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}

C++版本二

题解：链式前向星存边+欧拉回路

#include<iostream>
#include<cstdio>
#define M 50010
#define N 10010
using namespace std;
struct edge_node
{
    int to,next;
    bool vis;
}e[M*2];
int head[N];
int cnt;
void ins(int u,int v)
{
    e[++cnt].to = v; e[cnt].next = head[u]; head[u] = cnt;
    e[cnt].vis = false;
}
void find(int u)
{
    for (int i=head[u];i;i=e[i].next)
    {
        if (!e[i].vis)
        {
            e[i].vis = true;
            find(e[i].to);
        }
    }
    printf("%d\n",u);
}
int main()
{
    int n,m,u,v;
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;i++)
    {
        scanf("%d%d",&u,&v);
        ins(u,v);
        ins(v,u);
    }
    find(1);
}