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empty()

NULL空就返回1，其他返回0

bool empty() const noexcept;

This function does not modify the value of the string in any way. To clear the content of a string, see string::clear.

Parameters

Return Value

Example

// string::empty#include 
   
    #include 
    
     int main (){     std::string content;  std::string line;  std::cout << "Please introduce a text. Enter an empty line to finish:\n";  do {       getline(std::cin,line);    content += line + '\n';  } while (!line.empty());  std::cout << "The text you introduced was:\n" << content;  return 0;}
    
   

Edit & Run

This program reads the user input line by line and stores it into string content until an empty line is introduced.