#include  < map >
#include  < set >
#include  < string >
#include  < iostream >
#include  < fstream >
using   namespace  std;

void  initialize_exclusion_set( set < string >& );     // 初始化set容器,把要排除在外的单词插入其中
void  process_file(map < string , int >& , const   set < string >& ,ifstream &  );     // 从input.txt文件中读取单词,若单  词未在 set容器中出现过,将其置为map容器中的关键字key,并使相应key的value自加1, 否则读取下一单词,以空格为分界符
void  user_query( const  map < string , int >& );     // 用户控制台,用户输入search_word,若在map中存在则打印key与相应value值
void  display_word_count( const  map < string , int >& ,ofstream & );     // 输出map中的所有key与其相应的value值于output.txt中

int  main()
... {
    ifstream ifile("G:/input.txt");
    ofstream ofile("G:/output.txt");

    if(!ifile||!ofile)
    ...{
        cerr << "Unable to open file!!! ";
        return -1;
    }

    set<string> exclude_set;
    initialize_exclusion_set(exclude_set);

    map<string,int> word_count;
    process_file(word_count,exclude_set,ifile);
    user_query(word_count);
    display_word_count(word_count,ofile);

    return 0;
}

void  initialize_exclusion_set( set < string >&  exs)
... {
    static string _exclude_words[5]=...{
        "the","a","and","an","are"
    };

    exs.insert(_exclude_words,_exclude_words+5);
}

void  process_file(map < string , int >&  word_count,
           const   set < string >&  exclude_set,ifstream &  ifile )
... {
    string word;
    while(ifile>>word)
    ...{
        if(exclude_set.count(word))
            continue;
        word_count[word]++;
    }
}

void  user_query( const  map < string , int >   & word_map)
... {
    string search_word;
    cout << "Please enter a word to search : q to quit ";
    cin>>search_word;
    while(search_word!="q")
    ...{
        map<string,int>::const_iterator it;
        if((it=word_map.find(search_word))!=word_map.end())
            cout << "Found! "<<it->first
                 << " occurs "<<it->second
                 << " times. ";
        else cout<<search_word
             <<" was not found in text. ";
        cout<<" Another search?(q to quit)";
        cin>>search_word;

    }
}

void  
display_word_count( const  map < string , int >   & word_map,ofstream &  os)
... {
    map<string,int>::const_iterator 
        iter=word_map.begin(),
        end_it=word_map.end();
    while(iter!=end_it)
    ...{
        os<<iter->first <<"("
          <<iter->second<<")"<<endl;
        ++iter;
    }

    os<<endl;

}