std::vector<T,Allocator>::clear

void clear();

void clear() noexcept;

constexpr void clear() noexcept;

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 iterators are also invalidated.

Leaves the capacity() of the vector unchanged (note: the standard's restriction on the changes to capacity is in the specification of vector::reserve, see [1]).

Parameters

(none).

Return value

(none).

Complexity

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

Example

#include <algorithm>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> container{1, 2, 3};
 
    auto print = [](const int& n) { std::cout << " " << n; };
 
    std::cout << "Before clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << "\nSize=" << container.size() << ", Capacity=" << container.capacity() << '\n';
 
    std::cout << "Clear\n";
    container.clear();
 
    std::cout << "After clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << "\nSize=" << container.size() << ", Capacity=" << container.capacity() << '\n';
}

Before clear: 1 2 3
Size=3, Capacity=3
Clear
After clear:
Size=0, Capacity=3

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also