NYOJ 单词拼接

# include<iostream>
# include<string>
# include<string.h>
# include<queue>
# include<stdio.h>
# include<math.h>
#include <algorithm>
using namespace std;
#define MAX 2005
int first[MAX],next[MAX],u[MAX],v[MAX],used[MAX],h=,ct=,in[MAX],ans[MAX];
int out[MAX],x=;
string s[MAX];
char ch;
void AddEdge(int a,int b)
{
    u[h] = a;
    v[h] = b;
    out[a]++;
    in[b]++;
    next[h] = first[u[h]];
    first[u[h]] = h;
    h++;
}

int judge(int p)
{
    int count1 = ;
    int count2 = ;
    int vertex[];
    for(int i=;i<=p;i++)
    {
        if(out[i]-in[i] ==  )
        {
            if(count1>=)
                return -;
            vertex[] = i;
            count1++;
        }
        else if(out[i]-in[i] == - )
        {
            if(count2>=)
                return -;
            vertex[] = i;
            count2++;
        }
        else if(out[i]-in[i] == )
        {
            continue;
        }
        else            //WA原因
        {
            return -;
        }
    }
    if(count1== && count2==)
    {
        return vertex[];
    }
    else if(count1== && count2==)
    {
        for(int i=;i<=;i++)
        {
            if(in[i]!= && out[i]!=)
                return i;
        }
    }
    else
        return -;
}
void dfs(int k)        //k是出发顶点
{
    for(int i = ; i < h; i++)
    {
        if(u[i] == k)
        {
            //printf("%d %d\n------------\n",u[i],k);
            if(used[i]!=)
            {
                used[i] = ;
                dfs(v[i]);
                ans[ct++] = i;
                //printf("%d %d\n------------\n",ct,i);
                ///求出后答案是倒着的
            }
        }
    }

}
int main()
{
    int m,n,i,j;
    cin>>n;
    while(n--)
    {
        cin>>m;
        h = ;
        x = ;
        ct = ;
        for(i=;i<MAX;i++)
        {
            first[i] = -;
            next[i] = -;
            used[i] = ;
            in[i] = ;
            out[i] = ;
        } 

        for(i=;i<=m;i++)
        {
            cin>>s[i];
        }
        sort(s+,s+m+);
        for(i=;i<=m;i++)
        {
            int a,b;
            a = s[i][] - 'a' + ;
            b = s[i][ s[i].length()- ] - 'a' + ;
            //printf("%d %d",a,b);
            AddEdge(a,b);
        }
        int k,flag = ;
        k = judge();
        /*
        printf("%d\n------------------\n",k);

        for(i=1;i<h;i++)
                {
                   printf("%d %d %d\n",u[i],v[i],used[i]);
            }
        printf("\n------------------\n");
        */
        dfs(k);

        if(k==-)
        {
            flag = ;
        }
        else
        {
            for(i=;i<h;i++)
                {
                   if(used[i]!=)
                   {
                       flag = ;
                    break;
                }
            }
        }

        if(flag==)
        {
            for(i=ct-;i>=;i--)
            {
                if(i!=)
                    cout<<s[ans[i]]<<"." ;
                else
                    cout<<s[ans[i]];
            }
            cout<<endl;
        }
        else        printf("***\n");

    }
    return ;
}