C++关联容器综合应用:TextQuery小程序

本文介绍C++关联容器综合应用:TextQuery小程序(源自C++ Primer)。

关于关联容器的概念及介绍,请参考园子里这篇博文:http://www.cnblogs.com/cy568searchx/archive/2012/10/08/2715306.html

 #include<iostream>
#include<fstream>
#include<sstream>
#include<string>
#include<map>
#include<vector>
#include<set>
using namespace std;
//文本查询程序
class TextQuery
{
public:
typedef vector<string>::size_type line_no; void read_file(ifstream &is)
{
store_file(is);
build_map();
}
set<line_no> run_query(const string&) const;
string text_line(line_no) const;
private:
void store_file(ifstream&);
void build_map();
vector<string> lines_of_text;
map<string,set<line_no> > word_map;
};
void TextQuery::store_file(ifstream &is)
{
string textline;
while(getline(is,textline))
lines_of_text.push_back(textline);
}
void TextQuery::build_map()
{
//process each line
for(line_no line_num=;line_num!=lines_of_text.size();++line_num)
{
istringstream line(lines_of_text[line_num]);
string word;
while(line>>word)
//add thie line number to the set
//subscript will add word to the map if it's not already there
word_map[word].insert(line_num);
}
}
set<TextQuery::line_no> TextQuery::run_query(const string &query_word) const
{
//Note:must use find and not subscript the map directly
//to avoid adding words to word_map!
map<string,set<line_no> >::const_iterator loc=word_map.find(query_word);
if(loc==word_map.end())
return set<line_no>();//not found, return empty set.
else
return loc->second;
}
string TextQuery::text_line(line_no line) const
{
if(line<lines_of_text.size())
return lines_of_text[line];
throw out_of_range("line number out of range");
}
string make_plural(size_t ctr,const string &word,const string &ending)
{
return (ctr==)?word:word+ending;
}
void print_results(const set<TextQuery::line_no>& locs,const string& sought,const TextQuery& file)
{
typedef set<TextQuery::line_no> line_nums;
line_nums::size_type size=locs.size();
cout<<"\n"<<sought<<" occurs "
<<size<<" "
<<make_plural(size,"time","s")<<endl;
line_nums::const_iterator it=locs.begin();
for(;it!=locs.end();++it)
{
cout<<"\t(line "
<<(*it)+<<") "
<<file.text_line(*it)<<endl;
}
}
ifstream& open_file(ifstream &in,const string &file)
{
in.close();
in.clear(); in.open(file.c_str());
return in;
}
//program takes single argument specifying the file to query
int main(int argc,char **argv)
{
ifstream infile;
if(argc<||!open_file(infile,argv[]))
{
cerr<<"No input file!"<<endl;
return EXIT_FAILURE;
}
TextQuery tq;
tq.read_file(infile);//build query map
//iterate with the user:prompt for a word to find and print results
//loop indefinitely;the loop exit is inside the while
while(true)
{
cout<<"enter word to look for, or q to quit:";
string s;
cin>>s;
if(!cin||s=="q") break;
set<TextQuery::line_no> locs=tq.run_query(s);
//print count and all occurrences, if any
print_results(locs,s,tq);
}
return ;
}

运行结果:

C++关联容器综合应用:TextQuery小程序

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