查找字符串中正则表达式的所有匹配项的程序

先决条件：匹配| C++中的正则表达式(正则表达式)

给定一个正则表达式，任务是在字符串查找所有正则表达式匹配项。

• 不使用迭代器：

  // C++ program to find all the matches
  #include 
  using namespace std;
  int main()
  {
      string subject("My GeeksforGeeks is my " 
                      "GeeksforGeeks none of your GeeksforGeeks");
    
      // Template instantiations for
      // extracting the matching pattern.
      smatch match;
      regex r("GeeksforGeeks");
      int i = 1;
      while (regex_search(subject, match, r)) {
          cout << "\nMatched string is " << match.str(0) << endl
               << "and it is found at position " 
               << match.position(0)<

  输出：

  Matched string is GeeksforGeeks
  and it is found at position 3
  
  Matched string is GeeksforGeeks
  and it is found at position 7
  
  Matched string is GeeksforGeeks
  and it is found at position 14
  

  注意：上面的代码运行得很好，但是问题是输入字符串将丢失。

• 使用迭代器：
  对象可以通过调用具有三个参数的构造来构建：将字符串迭代指示搜索的开始位置，一个字符串迭代指示搜索的结束位置，和该正则表达式的对象。使用默认构造函数构造另一个迭代器对象，以获取序列结束迭代器。

  #include 
  using namespace std;
  int main()
  {
      string subject("geeksforgeeksabcdefghg"
                     "eeksforgeeksabcdgeeksforgeeks");
    
      // regex object.
      regex re("geeks(for)geeks");
    
      // finding all the match.
      for (sregex_iterator it = sregex_iterator(subject.begin(), subject.end(), re);
           it != sregex_iterator(); it++) {
          smatch match;
          match = *it;
          cout << "\nMatched  string is = " << match.str(0)
               << "\nand it is found at position "
               << match.position(0) << endl;
          cout << "Capture " << match.str(1)
               << " at position " << match.position(1) << endl;
      }
      return 0;
  }
  

  输出：

  Matched  string is = geeksforgeeks
  and it is found at position 0
  Capture for at position 5
  
  Matched  string is = geeksforgeeks
  and it is found at position 21
  Capture for at position 26
  
  Matched  string is = geeksforgeeks
  and it is found at position 38
  Capture for at position 43