reverse()

Library:  Algorithms

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An algorithm that reverses the order of elements in a sequence

#include <algorithm>

namespace std {
  template <class BidirectionalIterator>
  void reverse(BidirectionalIterator start,
               BidirectionalIterator finish);
}

The algorithm reverse() reverses the elements in a sequence so that the last element becomes the new first element, and the first element becomes the new last. For each non-negative integer i <= (finish - start)/2, reverse() applies iter_swap() to all pairs of iterators start + I, (finish - I) - 1.

reverse() performs exactly (finish - start)/2 swaps.

//
//  reverse.cpp
//

#include <algorithm>   // for reverse, reverse_copy
#include <vector>      // for vector
#include <iostream>    // for cout, endl
#include <iterator>    // for ostream_iterator



int main ()
{
    typedef std::vector<int, std::allocator<int> > Vector;
    typedef std::ostream_iterator<int, char,
                                  std::char_traits<char> >
            Iter;

    // Initialize a vector with an array of integers.
    const Vector::value_type a[] = { 1, 2, 3, 4, 5, 
                                     6, 7, 8, 9, 10 };

    Vector v (a + 0, a + sizeof a / sizeof *a);

    // Print out elements in original (sorted) order.
    std::cout << "Elements before reverse: \n     ";
    std::copy (v.begin (), v.end (), Iter (std::cout, " "));

    // Reverse the ordering.
    std::reverse (v.begin (), v.end ());

    // Print out the reversed elements.
    std::cout << "\n\nElements after reverse: \n     ";
    std::copy (v.begin (), v.end (), Iter (std::cout, " "));

    std::cout << "\n\nA reverse_copy to cout: \n     ";
    std::reverse_copy (v.begin (), v.end (), 
                       Iter (std::cout, " "));
    std::cout << std::endl;

    return 0;
}


Program Output:

Elements before reverse: 
     1 2 3 4 5 6 7 8 9 10 

Elements after reverse: 
     10 9 8 7 6 5 4 3 2 1 

A reverse_copy to cout: 
     1 2 3 4 5 6 7 8 9 10 

reverse_copy(), swap()

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.2.9