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

From cppreference.com
< cpp‎ | container‎ | vector
 
 
 
 
void assign( size_type count, const T& value );
(1) (constexpr since C++20)
template< class InputIt >
void assign( InputIt first, InputIt last );
(2) (constexpr since C++20)
void assign( std::initializer_list<T> ilist );
(3) (since C++11)
(constexpr since 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 [firstlast). 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 integral type.

(until C++11)

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

(since C++11)
3) Replaces the contents with the elements from the initializer list ilist.

All iterators (including the end() iterator) and all references to the elements are invalidated.

Contents

[edit] 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

[edit] Complexity

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

[edit] Example

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

#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

[edit] See also

assigns a range of values to the container
(public member function) [edit]
assigns values to the container
(public member function) [edit]