std::forward_list resize() method
- od C++11
// (1) Non const version only
void resize( size_type count );
// (2) Non const version only
void resize( size_type count, const value_type& value );
Resizes the container to contain count
elements.
If the current size is greater than count
, the container is reduced to its first count
elements.
If the current size is less than count:
- (1) Additional default-inserted elements are appended.
- (2) Additional copies of value are appended.
Parameters
count
- new size of the containervalue
- the value to initialize the new elements with
Type requirements
- (1) -
T
(the container's element type) must meet the requirements ofDefaultInsertable
. - (2) -
T
(the container's element type) must meet the requirements ofCopyInsertable
.
Return value
(none)
Complexity
Linear in the difference between the current size and count
- O(size() - count).
Additional complexity possible due to list traversal to reach the first element to erase/the end position to insert.
Exceptions
(none)
Notes
If value-initialization in overload (1) is undesirable, for example, if the elements are of non-class type and zeroing out is not needed,
it can be avoided by providing a custom Allocator::construct()
.
Example
#include <iostream>
#include <forward_list>
int main()
{
std::forward_list<int> c = {1, 2, 3};
std::cout << "The forward_list holds: ";
for (const auto& el: c) std::cout << el << ' ';
std::cout << '\n';
c.resize(5);
std::cout << "After resize up to 5: ";
for (const auto& el: c) std::cout << el << ' ';
std::cout << '\n';
c.resize(2);
std::cout << "After resize down to 2: ";
for (const auto& el: c) std::cout << el << ' ';
std::cout << '\n';
c.resize(6, 4);
std::cout << "After resize up to 6 (initializer = 4): ";
for (const auto& el: c) std::cout << el << ' ';
std::cout << '\n';
}
The forward_list holds: 1 2 3
After resize up to 5: 1 2 3 0 0
After resize down to 2: 1 2
After resize up to 6 (initializer = 4): 1 2 4 4 4 4
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