std::vector assign() method

since C++20

// (1) Non const version only
constexpr void assign( size_type count, const T& value );

// (2) Non const version only
template< class InputIt >
constexpr void assign( InputIt first, InputIt last );

// (3) Non const version only
constexpr void assign( std::initializer_list<T> ilist );

since C++11

// (1) Non const version only
void assign( size_type count, const T& value );

// (2) Non const version only
template< class InputIt >
void assign( InputIt first, InputIt last );

// (3) Non const version only
void assign( std::initializer_list<T> ilist );

until C++11

// (1) Non const version only
void assign( size_type count, const T& value );

// (2) Non const version only
template< class InputIt >
void assign( InputIt first, InputIt last );

Replaces the contents of the container with the contents of another.

• (1) Replaces the contents with count copies of value value.

• (2) Replaces the contents with copies of those in the range [ first, last ).

  Undefined Behavior

  The behavior is undefined

  if either argument is an iterator into *this.

  since C++11

  This overload participates in overload resolution only if InputIt satisfies LegacyInputIterator.

  until C++11

  This overload has the same effect as overload (1) if InputIt is an integral type.

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

Invalidation

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

Return value

(none)

Complexity

• (1) Linear in count - O(count).
• (2) Linear in distance between first and last - O(std::distance(firs,t last)).
• (3) Linear in ilist.size() - O(ilist.size()).

Exceptions

(none)

Examples

Main.cpp

#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