POJ

题解：直接欧拉回路套模板即可

#include<iostream>#include<cstring>#include<cstdio>#include<algorithm>using namespace std;const int mx = 5e4+5;struct node{    int u,v;    int next;    bool operator<(const node &a)const{        if(u!=a.u) u < a.u;        return v < a.v;    }}a[mx],E[mx<<1];int head[mx],vis[mx<<1],tot;void init(){    tot = 0;    memset(vis,0,sizeof(vis));    memset(head,0,sizeof(head));}void add(int u,int v){    tot++;    E[tot].u = u;    E[tot].v = v;    E[tot].next = head[u];    head[u] = tot;}void dfs(int u){    for(int i = head[u]; i; i = E[i].next){        int v = E[i].v;        if(!vis[i]){            vis[i] = 1;            dfs(v);        }    }    printf("%d\n",u);}int main(){    int n,m;    while(scanf("%d%d",&n,&m)!=EOF){        init();        for(int i = 0; i < m; i++){            int u,v;            scanf("%d%d",&u,&v);            add(u,v);            add(v,u);        }        dfs(1);    }    return 0;}