给定单词,看是否存在欧拉通路
http://poj.org/problem?id=1386
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn=26+5;
int fa[maxn];
int in[maxn],out[maxn];
int m;//单词数
int findset(int u)
{
if(fa[u]==-1) return u;
return fa[u]=findset(fa[u]);
}
int main()
{
int T; scanf("%d",&T);
while(T--)
{
memset(in,0,sizeof(in));
memset(out,0,sizeof(out));
memset(fa,-1,sizeof(fa));
scanf("%d",&m);
for(int i=0;i<m;i++)
{
char str[1200];
scanf("%s",str);
int len=strlen(str);
int u=str[0]-'a', v=str[len-1]-'a';
in[u]++;
out[v]++;
u=findset(u), v=findset(v);
if(u!=v) fa[u]=v;
}
int cnt=0;
for(int i=0;i<26;i++)
if( (in[i]||out[i]) && findset(i)==i ) cnt++;
if(cnt>1)
{
printf("The door cannot be opened.\n");
continue;
}
int c1=0, c2=0, c3=0;//分别表示入度!=出度时的三种情况
for(int i=0;i<26;i++)
{
if(in[i]==out[i]) continue;
else if(in[i]-out[i]==1) c1++;
else if(out[i]-in[i]==1) c2++;
else c3++;
}
if( ( (c1==c2&&c1==1)||(c1==c2&&c1==0) )&&c3==0 )
printf("Ordering is possible.\n");
else
printf("The door cannot be opened.\n");
}
return 0;
}