C++primer中的TextQuery（读取文本）

本题目对应于 C++primer（第四版）中第十章的文本查询类（TextQuery）

用到的知识有：

顺序容器 vector

关联容器 set，map

标准输入输出流，文件流，字符串流

//写一个文件 从文件中读单词 输出单词的次数和所在的行数

//...

#include <iostream>

#include <fstream>

#include <sstream>

#include <string>

#include <set>

#include <vector>

#include <map>

class TextQuery

{

public:

	typedef std::vector<std::string>::size_type line_no;

	//read the file

	void read_file(std::ifstream &is){

		store_file(is);

			build_map();

	}

	//query the file return the times every word appears

	std::set<line_no> run_query(const std::string&) const;

	//return the line-number of the word

	std::string text_line(line_no) const;

private:

	void store_file(std::ifstream &is);

	void build_map();

	std::vector<std::string> lines_of_text;

	std::map<std::string, std::set<line_no>> word_map;

};

void TextQuery::store_file(std::ifstream &is){

	std::string textline;

	while(std::getline(is, textline)){

		lines_of_text.push_back(textline);

	}

}

void TextQuery::build_map(){

	for(line_no line_num = 0; line_num != lines_of_text.size(); ++line_num){

		std::istringstream line(lines_of_text[line_num]);

		std::string word;

		while(line >> word){

			word_map[word].insert(line_num);

		}

	}

}

//read to get times of every word appears

std::set<TextQuery::line_no> TextQuery::run_query(const std::string& query_word) const{

	std::map<std::string, std::set<line_no>>::const_iterator loc = word_map.find(query_word);

	if(loc == word_map.end()){

		return std::set<line_no>();

	}

	else{

		return loc->second;

	}

}

//read to get the line-number of the word

std::string TextQuery::text_line(line_no line) const{

	if(line < lines_of_text.size()){

		return lines_of_text[line];

		throw std::out_of_range("line number out of range");

	}

};

std::string make_plural(size_t ctr, const std::string& word, const std::string& ending){

	return (ctr == 1) ? word : word + ending;

}

void print_results(const std::set<TextQuery::line_no>& locs, const std::string& sought, const TextQuery& file){

	typedef std::set<TextQuery::line_no> line_nums;

	line_nums::size_type size = locs.size();

	std::cout<< "\n" << sought << "occurs " << size << " " << make_plural(size, "time", "s") << std::endl;

	line_nums::const_iterator it = locs.begin();

	for(; it != locs.end(); ++it){

		std::cout << "\t(line" << (*it) + 1 << ")" <<file.text_line(*it) << std::endl;

	}

}

int main(){

	std::ifstream infile("F:\\input.txt");

	TextQuery tq;

	tq.read_file(infile);

	while(true){

		std::cout << "enter word to look for, or q to quit: ";

		std::string s;

		std::cin >> s;

		if(!std::cin || s == "q") break;

		// get the set of line numbers on which this word appears

		std::set<TextQuery::line_no> locs = tq.run_query(s);

		print_results(locs, s, tq);

	}

	return 0;

}

巴特西

C++primer中的TextQuery（读取文本）

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