从文本文件中读取输入并将其提取 - C++

Reading input from a text file and extracting it - C++

本文关键字：提取 C++ 输入 文本 文件 读取      更新时间：2023-10-16

我正在尝试逐行读取文本文件并将数据提取到我的程序中。 本质上，C++程序将读取已经制作的输入文件，该文件采用以下格式：

     Republican Senator John McMahon
     Democrat Mayor Steven Markel
     Republican Judge Matt Stevens
     Democrat Senator Anthony Quizitano
     S R
     M D
     J R
     ...
     ..
     ..

格式基本上是前 3 行包括政党、职位和姓名，接下来的行表示"结果"，其形式为：

[第一封立场信] [政党投票赞成]

因此，例如，如果您看到S R，这意味着参议员获得1票，然后投票给共和党候选人。

这是我到目前为止所拥有的：

            #include<fstream>
            int main()
            {
            std::ifstream input("file.txt");
            }

我的理解是，这将允许我输入文件，并逐行浏览它，但我不确定我应该如何从这里开始实现这一目标......有什么帮助吗？

谢谢！

为了好玩和荣耀，这是一个基于Boost Spirit的实现。我添加了更多虚假的投票输入，只是为了可以显示一些东西。

  • 我不确定候选人和选票之间是否存在1：1的关系（我不是美国公民，我不知道列出的候选人是否会投票或被投票）。所以我决定只使用假数据。

    const std::string input = 
    "Republican Senator John McMahonn"
    "Democrat Senator Anthony Quizitanon"
    "S Rn"
    "S Rn"
    "S Rn"
    "Democrat Mayor Steven Markeln"
    "Republican Judge Matt Stevensn"
    "M Dn"
    "J Rn"
    "S Rn"
    "S Rn";

    但是，该代码可以用于这两个目的。

  • 我使输入以什么顺序出现并不重要。
  • 但是，您可以选择断言单个字母 （S，M，J） 实际上对应于该点之前列出的位置。通过取消注释检查posletter_check来启用此功能

在 http://liveworkspace.org/code/d9e39c19674fbf7b2419ff88a642dc38 上观看现场演示

#define BOOST_SPIRIT_USE_PHOENIX_V3
#define BOOST_RESULT_OF_USE_DECLTYPE
#include <boost/fusion/adapted.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <iomanip>
namespace qi    = boost::spirit::qi;
namespace phx   = boost::phoenix;
struct Candidate { std::string party, position, name; };
BOOST_FUSION_ADAPT_STRUCT(Candidate, (std::string, party)(std::string, position)(std::string, name))
typedef std::map<std::pair<char, char>, size_t> Votes;
typedef std::vector<Candidate> Candidates;
template <typename It>
    struct parser : qi::grammar<It>
{
    mutable Votes _votes;
    mutable Candidates _candidates;
    parser() : parser::base_type(start)
    {
        using namespace qi;
        using phx::bind; using phx::ref; using phx::val;
        start = (line % eol) >> *eol >> eoi;
        line = 
              vote      [ phx::bind(&parser::register_vote, phx::ref(*this), _1) ]
            | candidate [ phx::push_back(phx::ref(_candidates), _1) ]
            ;
        vote %= graph   
                        // Comment the following line to accept any single
                        // letter, even if a matching position wasn't seen
                        // before:
                        [ _pass = phx::bind(&parser::posletter_check, phx::ref(*this), _1) ]  
            >> ' ' 
            >> char_("RD")
            ;
        candidate = (string("Republican") | string("Democrat"))
            >> ' ' 
            >> as_string [ +graph ]
            >> ' ' 
            >> as_string [ +(char_ - eol) ]
            ;
    }
  private:
    bool posletter_check(char posletter) const
    {
        for (auto& c : _candidates)
            if (posletter == c.position[0])
                return true;
        return false;
    }
    void register_vote(Votes::key_type const& key) const
    {
        auto it = _votes.find(key);
        if (_votes.end()==it)
            _votes[key] = 1;
        else
            it->second++;
    }
    qi::rule<It, Votes::key_type()> vote;
    qi::rule<It, Candidate()> candidate;
    qi::rule<It> start, line;
};
int main()
{
    const std::string input = 
        "Republican Senator John McMahonn"
        "Democrat Senator Anthony Quizitanon"
        "S Rn"
        "S Rn"
        "S Rn"
        "Democrat Mayor Steven Markeln"
        "Republican Judge Matt Stevensn"
        "M Dn"
        "J Rn"
        "S Rn"
        "S Rn";
    std::string::const_iterator f(std::begin(input)), l(std::end(input));
    parser<std::string::const_iterator> p;
    try
    {
        bool ok = qi::parse(f,l,p);
        if (ok)   
        {
            std::cout << "ncandidate listn";
            std::cout << "------------------------------------------------n";
            for (auto& c : p._candidates)
                std::cout << std::setw(20) << c.name << " (" << c.position << " for the " << c.party << "s)n";
            std::cout << "nVote distribution:n";
            std::cout << "------------------------------------------------n";
            for (auto& v : p._votes)
                std::cout << '(' << v.first.first << "," << v.first.second << "): " << v.second << " votes " << std::string(v.second, '*') << "n";
        }
        else std::cerr << "parse failed: '" << std::string(f,l) << "'n";
        if (f!=l) std::cerr << "trailing unparsed: '" << std::string(f,l) << "'n";
    } catch(const qi::expectation_failure<std::string::const_iterator>& e)
    {
        std::string frag(e.first, e.last);
        std::cerr << e.what() << "'" << frag << "'n";
    }
}

输出：

candidate list
------------------------------------------------
        John McMahon (Senator for the Republicans)
   Anthony Quizitano (Senator for the Democrats)
       Steven Markel (Mayor for the Democrats)
        Matt Stevens (Judge for the Republicans)
Vote distribution:
------------------------------------------------
(J,R): 1 votes *
(M,D): 1 votes *
(S,R): 5 votes *****
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