poj1041欧拉回路

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <string>
#include <iostream>
using namespace std;
const int maxn=2000;
int len;
int head[maxn];
struct Node
{
    int a;int b;int c;
}node[maxn];
struct edge
{
    int to;int val;int next;int op;int vis;
}e[maxn*maxn];

int add(int from,int to,int val)
{
    e[len].to=to;
    e[len].val=val;
    e[len].next=head[from];
    head[from]=len++;
    return len-1;
}
int n=0;
int sum;

int cmp(const Node &a,const Node &b)
{
    return a.c<b.c;
}
void dfs(int u)
{
    for(int i=head[u];i!=-1;i=e[i].next){
        if(!e[i].vis){
            e[i].vis=1;e[e[i].op].vis=1;
            int cc=e[i].to;
            dfs(cc);
            cout<<e[i].val<<" ";
        }
    }
}
int main()
{
    int a;int b;int c;
    int degree[maxn];
    while(scanf("%d%d",&a,&b),a||b){
        memset(degree,0,sizeof(degree));
        len=0;
        memset(head,-1,sizeof(head));
        sum=0;
        scanf("%d",&c); node[sum].a=a;node[sum].b=b;node[sum].c=c;
        sum++;if(a>n) n=a;if(b>n) b=n;
        while(scanf("%d%d",&a,&b),a||b){
            scanf("%d",&c);node[sum].a=a;node[sum].b=b;node[sum].c=c;
            sum++;if(a>n) n=a;if(b>n) n=b;
        }
        sort(node,node+sum,cmp);
        for(int i=0;i<sum;i++){
            int a=node[i].a;int b=node[i].b;int c=node[i].c;
            int cc=add(a,b,c);int cc1=add(b,a,c);
            degree[a]++;degree[b]++;
            e[cc].op=cc1;e[cc1].op=cc;
            e[cc].vis=e[cc1].vis=0;
        }
        int flag=0;
        for(int i=0;i<sum;i++){
            int a=node[i].a;int b=node[i].b;
            if((degree[a]&1)||(degree[b]&1)) {
                flag=1;break;
            }
        }
        if(!flag){
            dfs(1);
        }
        else
            cout<<"Round trip does not exist.";
        cout<<endl;
    }
    return 0;
}