hdu 1116 Play on Words

http://acm.hdu.edu.cn/showproblem.php?pid=1116

欧拉通路和欧拉回路

#include <cstdio>
#include <cstring>
#include <algorithm>
#define maxn 1000
using namespace std;

int f[maxn],in[maxn],ou[maxn],a[maxn];
bool vis[maxn];
int n;
char str[maxn];

int find(int x)
{
    if(x==f[x]) return x;
    return f[x]=find(f[x]);
}

void union1(int x,int y)
{
    int fx=find(x);
    int fy=find(y);
    if(fx!=fy)
    f[fx]=fy;
}

void inti()
{
    for(int i=0; i<26; i++)
    f[i]=i;
}

int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        inti();
        memset(in,0,sizeof(in));
        memset(ou,0,sizeof(ou));
        memset(vis,false,sizeof(vis));
        for(int i=0; i<n; i++)
        {
            scanf("%s",str);
            int k=strlen(str);
            ou[str[0]-'a']++;
            in[str[k-1]-'a']++;
            vis[str[0]-'a']=true;
            vis[str[k-1]-'a']=true;
            union1(str[0]-'a',str[k-1]-'a');
        }
        int ans=0;
        for(int i=0; i<26; i++)
        {
            if(vis[i]&&f[i]==i)
              ans++;
        }
        if(ans>1)
        {
            printf("The door cannot be opened.
");
            continue;
        }
        int m1=0,m2=0;
        bool flag=true;
        for(int j=0; j<26; j++)
        {
            if(vis[j]&&in[j]!=ou[j])
            {
                if(in[j]-ou[j]==1)
                {
                    m1++;
                }
                else if(ou[j]-in[j]==1)
                {
                    m2++;
                }
                else flag=false;
            }
        }
        if(flag&&((m1==0&&m2==0)||(m1==1&&m2==1)))
        printf("Ordering is possible.
");
        else
        printf("The door cannot be opened.
");
    }
    return 0;
}