poj2337欧拉回路

对字符串从小到大排序，邻接表正向插入。

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <algorithm>

#include <cmath>

#include <stack>

#include <queue>

#include <vector>

#include <map>

#include <string>

#include <iostream>

using namespace std;

const int maxn=2222;



int cmp(const string &a,const string &b)

{

    return a<b;

}



struct Node

{

    int to;int val;int vis;

};

string str[maxn];

vector<Node> head[maxn];

int vis[maxn];

int father[100];

void add(int from,int to,int val,int vis )

{

    Node k; k.to=to; k.val=val;k.vis=vis;

    head[from].push_back(k);

}



int getfather(int x)

{

    if(x!=father[x]) father[x]=getfather(father[x]);

    return father[x];

}



void link(int a,int b)

{

    int fa=getfather(a);int fb=getfather(b);

    father[fa]=fb;

}

stack<string >  q;

void dfs(int x)

{

    int len=head[x].size();

        for(int i=0;i<len;i++){

        if(!head[x][i].vis){

            //cout<<x<<" "<<head[x][i].to<<endl;

            head[x][i].vis=1;

            dfs(head[x][i].to);

            q.push(str[head[x][i].val]);

        }

    }

}

void output()

{

    string a= q.top(); q.pop();

    cout<<a;

    while(!q.empty()){

        cout<<"."<<q.top();

        q.pop();

    }

}

int in[100];

int out[100];

int main()

{

    int Icase;

    cin>>Icase;

    int n;

    while(Icase--){

        memset(vis,0,sizeof(vis));

        for(int i=0;i<26;i++)

            father[i]=i;

        memset(in,0,sizeof(in));

        memset(out,0,sizeof(out));

        for(int i=0;i<=maxn;i++)

            head[i].clear();

        cin>>n;

        for(int i=0;i<n;i++)

            cin>>str[i];

        sort(str,str+n,cmp);

        for(int i=0;i<n;i++){

            int a=str[i][0]-'a'; int len=str[i].size();int b=str[i][len-1]-'a';

            add(a,b,i,0); vis[a]=1;vis[b]=1; in[b]++;out[a]++; link(a,b);

        }

        int ans=0;

        for(int i=0;i<26;i++)

            if(vis[i]) if(i==father[i]) ans++;

        int flag=0;int in1=0;int out1=0;int sign;int sign1;

        for(int i=0;i<26;i++)

        if(vis[i]) {

            sign1=i;break;

        }

        for(int i=0;i<26;i++)

        if(vis[i]){

            if(in[i]==out[i]) continue;

            if(in[i]-out[i]==1){

                in1++;

            }

            if(out[i]-in[i]==1){

                out1++; sign=i;

            }

            if(out[i]-in[i]>1||out[i]-in[i]>1){

                flag=1;break;

            }

        }

        //cout<<sign<<endl;system("pause");

        if(!flag) if(in1>1||out1>1) flag=1;

        if(ans!=1||flag) cout<<"***"<<endl;

        else{

            if(in1!=0) dfs(sign);

            else dfs(sign1);

            output();

            cout<<endl;

        }

    }

    return 0;

}