ccf 送货

#include<iostream>
#include<cstring>
#include<cstdio>
#include<queue>
#include<vector>
using namespace std;
vector<int> a[1001];
int main(){
int n,m,x,y,count=0;
scanf("%d%d",&n,&m);
memset(a,0,sizeof(a));
for(int i=0;i<m;i++){
scanf("%d%d",&x,&y);
a[x][y]=a[y][x]=1;
}
int path[10001],k=1;
queue<int> q;
q.push(1);
path[0]=1;
while(!q.empty()){
int tmp=q.front();
q.pop();
for(int i=1;i<=n;i++){
if(a[tmp][i]){
a[tmp][i]=a[i][tmp]=0;
count++;
path[k++]=i;
q.push(i);
break;
}
}
}
if(count==m){
cout<<path[0];
for(int i=1;i<k;i++){
cout<<' '<<path[i];
}
cout<<endl;
}
else{
cout<<-1<<endl;
}
return 0;
}