View Code of Problem 1082

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <stack>
#include <algorithm>
#include <cmath>
#include <map>
#define LL long long
#define DB double

using namespace std;
const int N = 1009;
char ch[N][22];
struct LT{
    int to,nex;
    int p;
}L[N<<1];
int F[150],cnt;
int v[N<<1],n;
int in[150];
void add(int f,int t,int p)
{
    L[cnt].nex = F[f];L[cnt].to = t;
    L[cnt].p = p; F[f] = cnt++;
}
int ou;
void dfs(int k,int p)
{
    for(int i=F[k];i;i=L[i].nex)
    {
        int to = L[i].to;
        if(!v[i])
        {
            v[i] = 1;
            dfs(to,L[i].p);
        }
    }
    if(ou&&p>=0) printf(" ");else ou = 1;
    if(p!=-1)
    printf("%s",ch[p]);
}
int visit[150];
void dfs1(int k)
{
    if(!visit[k]) return ;
    visit[k] = 0;
    for(int i=F[k];i;i=L[i].nex)
    {
        dfs1(L[i].to);
    }
}
void solve(int T)
{
    int c=0,f=-1;
    for(int i=0;i<150;i++)
    if(in[i]!=0)
    {
        if(in[i]==0) continue;
        if(in[i]==1||in[i]==-1)
        c++;
        else
        c = 10;
        if(in[i]==1)
        f = i;
    }
    if(f==-1)
        f = ch[0][0];
    dfs1(f);
    for(int i=0;i<150;i++) if(visit[i]) c=10;
    if(c>2){printf("Case %d: No\n",T);return;}
    printf("Case %d: Yes\n",T);
    memset(v,0,sizeof(v));
    ou = 0;
    dfs(f,-1);
    printf("\n");
}
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
    #endif
    int cas,T=1;scanf("%d",&cas);
    while(cas--)
    {
        scanf("%d",&n);
        memset(F,0,sizeof(F));
        memset(in,0,sizeof(in));
        cnt = 1;
        memset(visit,0,sizeof(visit));
        for(int i=0;i<n;i++)
        {
            scanf("%s",ch[i]);
            int a= ch[i][0],b=ch[i][strlen(ch[i])-1];
            add(b,a,i);
            visit[a] = visit[b] =  1;
            in[a]--,in[b]++;
        }
        solve(T);T++;
    }
    return 0;
}