如何从txt文件c++中提取括号之间的数字

How can I extract numbers between a parenthesis from a txt file c++?

本文关键字：之间 数字 提取 txt 文件 c++      更新时间：2023-10-16

我的问题是：我的逻辑有一些问题。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：年份：2008-2次，年份：2010-2次等。PD：谢谢，我很无聊。

#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-Zs]*,?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;
}

您可以使用std::regex_search方法来匹配行。但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-Zs]*,?s*([0-9]+)))"); // For the regex: ([a-zA-Zs]*,?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;
}

对于OP的任务，一个简单的循环可以完成遍历字符串中所有字符的工作。从而管理两种状态：

  • open。。。true在'('之后和')'之前，否则为false
  • number。。。CCD_ 8，而CCD_ 9是CCD_

当number是true时，收集数字并组合为int。如果在number为true时找到非数字，则这是数字的末尾，并存储该值。

号码的检查也可以在行尾完成。在这种特定情况下，这意味着语法错误，因为这意味着缺少右括号()(。(OP没有说明如何处理。(

我的样本代码：

#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"
"Referencesn"
"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

coliru上的实时演示

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