CCF 201512-4 送货（欧拉路径+字典序最小）

#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <iostream>
using namespace std;
#define maxn 200100
bool  flag[10010][10010];
int  n,m,tot,cnt;
int head[maxn];
int ans[10000000];
int degree[maxn];
struct Road
{
int u,v,next;
}edge[maxn];
struct node
{
int u,v,sum;
}road[maxn];
bool comp(node a,node b)
{
return a.sum>b.sum;
}
void build(int u,int v)
{
edge[tot].u=u;
edge[tot].v=v;
edge[tot].next=head[u];
head[u]=tot++;
}
void dfs(int x)
{
int i;
for(i=head[x];i!=-1;i=edge[i].next)
{
int t1=edge[i].u,t2=edge[i].v;
if(flag[t1][t2]==0 && flag[t2][t1]==0)
{
flag[t1][t2]=1;
flag[t2][t1]=1;
dfs(t2);
}
}
ans[++cnt]=x;
return ;
}
bool check()
{
for(int i=0;i<tot;i++)
{
int t1=edge[i].u,t2=edge[i].v;
if(flag[t1][t2]==0 && flag[t2][t1]==0)
return 0;
}
return 1;
}
int  main()
{
int  i,j;
while(scanf("%d%d",&n,&m)!=EOF)
{
int tail=0;int num=0;
memset(head,-1,sizeof(head));
memset(degree,0,sizeof(degree));
memset(flag,0,sizeof(flag));
for(i=0;i<m;i++)
{
int u,v;
scanf("%d%d",&u,&v);
road[tail].u=u;road[tail].v=v;
road[tail++].sum=u+v;
degree[u]++;
degree[v]++;
}
sort(road,road+tail,comp);
tot=0;cnt=0;
for(i=0;i<tail;i++)
{
build(road[i].u,road[i].v);
build(road[i].v,road[i].u);
}
for(i=1;i<=n;i++)
if(degree[i]%2==1)
num++;
if(!(num==0 || num==2))
{
printf("-1\n");
continue;
}
dfs(1);
if (!check())
{
cout << "-1\n";
continue;
}
cout << ans[cnt];
for(i=cnt-1;i>0;i--)
cout << " " << ans[i];
cout << endl;
}
return 0;
}