給定單詞,看是否存在尤拉通路

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;//單詞數
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;//分別表示入度!=出度時的三種情況
        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;
}