Question

我的问题是这样的：我的逻辑有些问题。我已经检测到何时带有括号，但是现在我需要查找数字并知道它们在txt文件中重复多少次。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.

结果应为：年：2008-2次，年：2010-2次，依此类推。 PD：谢谢，我非常菜鸟。

#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方法来匹配行。但是请记住在文件顶部包含#include <regex>。

#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;
}

Answer 2

对于OP的任务，可以执行一个简单的循环来遍历字符串的所有字符。因此，可以管理两个状态：

open ... true在'('之后和')'之前，否则为假
number ... true，当open为true时找到数字。

虽然number是true位数字，但会被收集并组合到int中。如果在number为true时发现非数字，则该数字为数字的末尾并存储该值。

号码的检查也可以在行尾进行。在此特定情况下，这将意味着语法错误，因为这意味着缺少右括号（)）。（OP并未声明如何处理。）

我的示例代码：

#include <iostream>
#include <sstream>
#include <vector>
#include <map>

std::vector<int> parseLine(const std::string &text)
{
  bool open = false, number = false;
  std::vector<int> values; int value = 0;
  for (char c : text) {
    switch (c) {
      case '(': open = true; break;
      case ')': open = false;
      default:
        if (open && c >= '0' && c <= '9') {
          number = true;
          (value *= 10) += (c - '0'); // value = 10 * value + (c - '0')
        } else if (number) {
          values.push_back(value);
          value = 0; number = false;
        }
    }
  }
  if (number) {
    values.push_back(value);
    std::cerr << "ERROR: Missing ')' at line end!\n";
  }
  return values;
}

const std::string text =
"(Visual basic)\n"
"(Llorente)\n"
"(Porto, 2008)\n"
"(Sommerville, 2010)\n"
"References\n"
"Visual Basic. (s.f.). Navarra.\n"
"Llorente, P.B. (s.f.). Fortran.\n"
"Porto, J.P. (2008)\n"
"Sommerville, I. (2010). Software Engineering. Unite Kingdom: Pearson.\n";

int main()
{
  // open file
  std::istringstream in(text);
  // parse/process file line by line
  std::map<int, int> histo;
  for (std::string line; std::getline(in, line);) {
    const std::vector<int> values = parseLine(line);
    // count occurrences of values
    for (int value : values) ++histo[value];
  }
  // report
  std::cout << "Report:\n";
  for (const std::pair<int, int> &entry : histo) {
    std::cout << entry.first << ": " << entry.second << '\n';
  }
  // done
  return 0;
}

输出：

Report:
2008: 2
2010: 2

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如何从C ++的txt文件中提取括号之间的数字？

2 个答案: