std::map::clear(3)

NAME
std::map::clear - std::map::clear

Synopsis
   void clear(); (noexcept since C++11)
   Erases all elements from the container. After this call, size() returns zero.
   Invalidates any references, pointers, and iterators referring to contained elements.
   Any past-the-end iterator remains valid.

Parameters
   (none)

Return value
   (none)

Complexity
   Linear in the size of the container, i.e., the number of elements.

Example
// Run this code
 #include <iostream>
 #include <string_view>
 #include <map>
 void print_info(std::string_view rem, const std::map<int, char>& v)
 {
     std::cout << rem << "{ ";
     for (const auto& [key, value] : v)
         std::cout << '[' << key << "]:" << value << ' ';
     std::cout << "}\n";
     std::cout << "Size=" << v.size() << '\n';
 }
 int main()
 {
     std::map<int, char> container{{1, 'x'}, {2, 'y'}, {3, 'z'}};
     print_info("Before clear: ", container);
     container.clear();
     print_info("After clear: ", container);
 }

Output:
 Before clear: { [1]:x [2]:y [3]:z }
 Size=3
 After clear: { }
 Size=0
  Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
     DR Applied to Behavior as published Correct behavior
   LWG 224 C++98 the complexity was log(size()) + N, but N corrected to 'linear in
                      was not defined size()'

See also
   erase erases elements
         (public member function)