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std::map<Key,T,Compare,Allocator>::clear

From cppreference.com
< cpp‎ | container‎ | map
 
 
Containers library
Sequence
(C++11)
Associative
Unordered associative
Adaptors
Views
(C++20)
 
 
void clear();
(until C++11)
void clear() noexcept;
(since C++11)

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

Invalidates any references, pointers, or iterators referring to contained elements. Any past-the-end iterator remains valid.

Contents

[edit] Parameters

(none)

[edit] Return value

(none)

[edit] Complexity

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

[edit] Example

#include <algorithm>
#include <iostream>
#include <map>
 
int main()
{
    std::map<int, char> container{{1, 'x'}, {2, 'y'}, {3, 'z'}};
 
    auto print = [](std::pair<const int, char>& n) { 
        std::cout << " " << n.first << '(' << n.second << ')'; 
    };
 
    std::cout << "Before clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << "\nSize=" << container.size() << '\n';
 
    std::cout << "Clear\n";
    container.clear();
 
    std::cout << "After clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << "\nSize=" << container.size() << '\n';
}

Output:

Before clear: 1(x) 2(y) 3(z)
Size=3
Clear
After clear:
Size=0


[edit] See also

erases elements
(public member function) [edit]