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Showing content from https://www.tutorialspoint.com/cpp_standard_library/cpp_algorithm_copy_n.htm below:

C++ Algorithm: copy_n Function

The C++ function std::algorithm::copy_n() copies first n numbers to a new location. If value of n is negative then function does nothing.

Following is the declaration for std::algorithm::copy_n() function form std::algorithm header.

template <class InputIterator, class Size, class OutputIterator>
OutputIterator copy_n (InputIterator first, Size n, OutputIterator result);

• first − Input iterators to the initial positions of the searched sequence.

• n − Number of elements to copy.

• result − Output iterator to the initial position in the new sequence.

Returns an iterator to the end of the destination range where elements have been copied.

Throws an exception if either element assignment or an operation on an iterator throws exception.

Please note that invalid parameters cause undefined behavior.

Linear in the distance between first to last.

The following example shows the usage of std::algorithm::copy_n() function.

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main(void) {
   vector<int> v1 = {1, 2, 3, 4, 5};
   vector<int> v2(3);

   copy_n(v1.begin(), 3, v2.begin());

   cout << "Vector v2 contains following elements" << endl;

   for (auto it = v2.begin(); it != v2.end(); ++it)
      cout << *it << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Vector v2 contains following elements
1
2
3

algorithm.htm

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