c++ - 如何从 txt 文件 c++ 中提取括号之间的数字？

Question

我的问题是:我的逻辑有问题。我已经检测到它何时有括号，但现在我需要找到数字并知道它们在 txt 文件中重复了多少次。这是我的 txt 文件:

(Visual basic)
(Llorente)
(Porto, 2008)
(Sommerville, 2010)
References
Visual Basic. (s.f.). Navarra.
Llorente, P.B. (s.f.). Fortran.
Porto, J.P. (2008)
Sommerville, I. (2010). Software Engineering. Unite Kingdom: Pearson.

结果应该是:year : 2008 - 2 times, year : 2010 - 2 times, etc.PD:谢谢，我很菜鸟。

#include <regex>
#include <iostream>
#include <fstream>
#include <map>
//33
int main()
{
    std::ifstream readStream("references.txt");
    std::map<int, int> cMap; 
    std::string input;
    std::regex reg(R"(\([a-zA-Z\s]*,?\s*([0-9]+)\))");
    std::regex inte("(\\+|-)?[[:digit:]]+");

    ///333
    while (std::getline(readStream, input)) {
            std::match_results < std::string::const_iterator > m;
    if ((std::regex_search(input, m, reg)) ) {
        int year = std::stoi(m[1]); 
        auto value = cMap.find(year);
        if (value != cMap.end()) { 
            cMap[value->first] = value->second + 1;
        } else {
            cMap[year] = 1; 
        }
    }



}
//33
for (auto x : cMap) { 
    std::cout << "year " << x.first << " is - " << x.second << " times." << std::endl;
}
//3
return 0;
}

Answer 1

您可以使用 std::regex_search匹配线的方法。但记得包括 #include <regex>在文件的顶部。

#include <regex>
#include <iostream>
#include <fstream>
#include <map>


int main()
{
    std::ifstream readStream("path/to/your/Example.txt");
    std::map<int, int> countMap; // Map containing (year, count) value pairs.
    std::string in;
    std::regex reg(R"(\([a-zA-Z\s]*,?\s*([0-9]+)\))"); // For the regex: \([a-zA-Z\s]*,?\s*([0-9]+)\)

    while (std::getline(readStream, in)) {
        std::match_results < std::string::const_iterator > m;
        if (std::regex_search(in, m, reg)) { // If the current line matches our regex pattern.
            int year = std::stoi(m[1]); // The second element of the array contains our string representing the year.

            auto val = countMap.find(year);
            if (val != countMap.end()) { // If the year is already in the countMap we want to increment it.
                countMap[val->first] = val->second + 1;
            } else {
                countMap[year] = 1; // year doesn't exist in the countMap, it is the first time.
            }
        }
    }

    for (auto x : countMap) { // x is of type std::pair<int, int> which is our (year, count) value pair
        std::cout << "year " << x.first << " is - " << x.second << " times." << std::endl;
    }

    return 0;
}