C++ - 在文件中 查找 指定的词 出现的行号 (shared_ptr)

在文件中 查找 指定的词 出现的行号 (shared_ptr)

 
在一个指定的文本中, 查找相应的词, 并输出词出现的行号, 和具体的行, 不重复出现行.
由于传输的文本较大, 所以使用指针进行传递, 智能指针的"shared_ptr".
代码来自"C++ Primer"; 具体细节, 详见代码注释;
代码:/*
* cppprimer.cpp
*
* Created on: 2013.11.7
* Author: Caroline
*/

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
#include <memory>

#include <set>
#include <map>

using namespace std;

class QueryResult;
std::ostream& print(std::ostream& os, const QueryResult &qr);

class TextQuery {
public:
using line_no = std::vector<std::string>::size_type;
TextQuery(std::ifstream& );
QueryResult query(const std::string& ) const;
private:
std::shared_ptr<std::vector<std::string> > file; //文件内容
std::map<std::string, std::shared_ptr<std::set<line_no> > > wm; //词和行号的集合
};

/*把每一行放入text, 存入file(vector), 组成word和行号(set)的映射*/
TextQuery::TextQuery(std::ifstream &is) : file(new std::vector<std::string>)
{
std::string text;
while (std::getline(is, text)) {
file->push_back(text);
int n = file->size() - 1;
std::istringstream line(text);
std::string word;
while (line >> word) {
auto& lines = wm[word];
if (!lines)
lines.reset(new set<line_no>);
lines->insert(n);
}
}
}

class QueryResult {
friend std::ostream& print (std::ostream&, const QueryResult& );
public:
using line_no = std::vector<std::string>::size_type;
QueryResult (std::string s,
std::shared_ptr<std::set<line_no>> p,
std::shared_ptr<std::vector<std::string>> f) :
sought(s), lines(p), file(f) {}
private:
std::string sought; //查找字符串
std::shared_ptr<std::set<line_no>> lines; //行号集合
std::shared_ptr<std::vector<std::string>> file; //文件集合
};

/*找到指定sought的集合, 返回迭代器, 传入string和set*/
QueryResult TextQuery::query(const std::string& sought) const {
static std::shared_ptr<std::set<line_no>> nodata(new std::set<line_no>);
auto loc = wm.find(sought);
if (loc == wm.end())
return QueryResult(sought, nodata, file); //没有找到, 不打印
else
return QueryResult(sought, loc->second, file); //按行号打印
};

std::string make_plural (std::size_t ctr, const std::string& word,
const std::string ending)
{
return (ctr > 1) ? word + ending : word;
}

std::ostream& print(std::ostream& os, const QueryResult &qr){
os << qr.sought << " occurs " << qr.lines->size() << " "
<< make_plural(qr.lines->size(), "time", "s") << std::endl;
for(auto num : *qr.lines)
os << "\t(line " << num+1 << ") " << *(qr.file->begin()+num) << std::endl;
return os;
}

void runQueries (std::ifstream &infile) {
TextQuery tq(infile);
while (true) {
std::cout << "enter word to look for, or q to quit: ";
std::string s;
if ( !(cin>>s) || s == "q" ) break;
print(std::cout, tq.query(s)) << std::endl;
}
}

int main (void) {

std::ifstream infile;
infile.open("file.txt");
runQueries(infile);
infile.close();

return 0;

}

输出: