NAME¶

std::vector::clear - std::vector::clear

Synopsis¶

void clear(); (noexcept since C++11)
(constexpr since C++20)

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 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 reserve(), see SO).

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 <vector>

void print_info(std::string_view rem, const std::vector<int>& v)
{
std::cout << rem << "{ ";
for (const auto& value : v)
std::cout << value << ' ';
std::cout << "}\n";
std::cout << "Size=" << v.size() << ", Capacity=" << v.capacity() << '\n';
}

int main()
{
std::vector<int> container{1, 2, 3};
print_info("Before clear: ", container);
container.clear();
print_info("After clear: ", container);
}

Output:¶

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

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 2231 C++11 complexity guarantee was mistakenly complexity reaffirmed as
omitted in C++11 linear

See also¶

erase erases elements
(public member function)