std::map<Key,T,Compare,Allocator>::clear - cppreference.com (original) (raw)

| void clear(); | | (noexcept since C++11) (constexpr since C++26) | | ------------- | | ---------------------------------------------- |

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.

[edit] Complexity

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

[edit] Example

#include #include #include   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.

[edit] See also