std::fill_n

 

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Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n removeremove_if remove_copyremove_copy_if	replacereplace_if replace_copyreplace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffleshuffle  (C++11) unique unique_copy
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Defined in header <algorithm>
template< class OutputIt, class Size, class T > void fill_n( OutputIt first, Size count, const T& value );		(until C++11)
template< class OutputIt, class Size, class T > OutputIt fill_n( OutputIt first, Size count, const T& value );		(since C++11)

Assigns the given value value to the first count elements in the range beginning at first if count > 0. Does nothing otherwise.

Parameters

first	-	the beginning of the range of elements to modify
count	-	number of elements to modify
value	-	the value to be assigned
Type requirements
- OutputIt must meet the requirements of OutputIterator.

Return value

(none)	(until C++11)
Iterator one past the last element assigned if count > 0, first otherwise.	(since C++11)

Complexity

Exactly count assignments, for count > 0.

Possible implementation

template<class OutputIt, class Size, class T> OutputIt fill_n(OutputIt first, Size count, const T& value) { for (Size i = 0; i < count; i++) { *first++ = value; } return first; }

Example

The following code uses fill_n() to assign -1 to the first half of a vector of integers:

Run this code

#include <algorithm>
#include <vector>
#include <iostream>
 
int main()
{
    std::vector<int> v1{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
 
    std::fill_n(v1.begin(), 5, -1);
 
    for (std::vector<int>::iterator it = v1.begin(); it != v1.end(); ++it) {
        std::cout << *it << " ";
    }
    std::cout << "\n";
}

Output:

-1 -1 -1 -1 -1 5 6 7 8 9

See also

fill	assigns a range of elements a certain value (function template)