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std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>::clear - cppreference.com

From cppreference.com

void clear() noexcept;

 (since C++23)

Erases all elements from the container adaptor. After this call, size() returns zero.

Invalidates any references, pointers, and iterators referring to contained elements.

Complexity

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

Example

#include <iostream>
#include <string_view>
#include <flat_map>

void print_info(std::string_view rem, const std::flat_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::flat_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

See also