[英]Reading input from a text file and extracting it - C++
我正在嘗試逐行讀取文本文件並將數據提取到程序中。 本質上,C ++程序將讀取以下格式的輸入文件:
Republican Senator John McMahon
Democrat Mayor Steven Markel
Republican Judge Matt Stevens
Democrat Senator Anthony Quizitano
S R
M D
J R
...
..
..
格式基本上是前三行,包括“聚會”,“職位”和“姓名”,接下來的幾行表示“結果”,其形式為:
[第一份立場書] [當事方投票]
因此,例如,如果您看到SR,則表示參議員需要1票,而該票將由共和黨候選人獲得。
這是我到目前為止的內容:
#include<fstream>
int main()
{
std::ifstream input("file.txt");
}
我的理解是,這將允許我輸入文件並逐行處理它,但是我不確定如何從此處實現此目標……有什么幫助嗎?
謝謝!
出於樂趣和榮耀,這是基於Boost Spirit的實現。 我添加了更多的虛假投票輸入,只是為了顯示某些內容。
我不確定候選人與選票之間是否存在1:1的關系(我不是美國公民,也不知道所列候選人是會投票還是會被投票)。 所以我決定只使用假數據。
const std::string input = "Republican Senator John McMahon\\n" "Democrat Senator Anthony Quizitano\\n" "SR\\n" "SR\\n" "SR\\n" "Democrat Mayor Steven Markel\\n" "Republican Judge Matt Stevens\\n" "MD\\n" "JR\\n" "SR\\n" "SR\\n";
但是,該代碼可同時用於兩種目的。
posletter_check
取消對支票的注釋來啟用此posletter_check
在http://liveworkspace.org/code/d9e39c19674fbf7b2419ff88a642dc38上觀看現場演示
#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 McMahon\n"
"Democrat Senator Anthony Quizitano\n"
"S R\n"
"S R\n"
"S R\n"
"Democrat Mayor Steven Markel\n"
"Republican Judge Matt Stevens\n"
"M D\n"
"J R\n"
"S R\n"
"S R\n";
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 list\n";
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";
}
}
輸出:
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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