NAME¶

std::vector::assign - std::vector::assign

Synopsis¶

void assign( size_type count, const T& value ); (until
C++20)
constexpr void assign( size_type count, const T& (since
value ); C++20)
template< class InputIt > (until
void assign( InputIt first, InputIt last ); C++20)
template< class InputIt > (since
constexpr void assign( InputIt first, InputIt last (1) C++20)
);
(2) (since
void assign( std::initializer_list<T> ilist ); C++11)
(3) (until
C++20)
constexpr void assign( std::initializer_list<T> (since
ilist ); C++20)

Replaces the contents of the container.

1) Replaces the contents with count copies of value value
2) Replaces the contents with copies of those in the range [first, last). The
behavior is undefined if either argument is an iterator into *this.

This overload has the same effect as overload (1) if InputIt is an (until C++11)
integral type.
This overload participates in overload resolution only if InputIt (since C++11)
satisfies LegacyInputIterator.

3) Replaces the contents with the elements from the initializer list ilist.

All iterators, pointers and references to the elements of the container are
invalidated. The past-the-end iterator is also invalidated.

Parameters¶

count - the new size of the container
value - the value to initialize elements of the container with
first, last - the range to copy the elements from
ilist - initializer list to copy the values from

Complexity¶

1) Linear in count
2) Linear in distance between first and last
3) Linear in ilist.size()

Example¶

The following code uses assign to add several characters to a std::vector<char>:

// Run this code

#include <vector>
#include <iostream>
#include <string>

int main()
{
std::vector<char> characters;

auto print_vector = [&](){
for (char c : characters)
std::cout << c << ' ';
std::cout << '\n';
};

characters.assign(5, 'a');
print_vector();

const std::string extra(6, 'b');
characters.assign(extra.begin(), extra.end());
print_vector();

characters.assign({'C', '+', '+', '1', '1'});
print_vector();
}

Output:¶

a a a a a
b b b b b b
C + + 1 1

See also¶

constructor constructs the vector
(public member function)