reverse_copy

Algorithm

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• Synopsis
• Description
• Complexity
• Example
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Reverses the order of elements in a collection while copying them to a new collection.

None

#include <algorithm>
template <class BidirectionalIterator, class OutputIterator>
OutputIterator reverse_copy (BidirectionalIterator first,
                             BidirectionalIterator last,
                             OutputIterator result);

The reverse_copy algorithm copies the range [first, last) to the range [result, result + (last - first)) such that for any non- negative integer i < (last - first), the following assignment takes place:

*(result + (last - first) -i) = *(first + i)

reverse_copy returns result + (last - first). The ranges [first, last) and [result, result + (last - first)) must not overlap.

reverse_copy performs exactly (last - first) assignments.

//
// reverse.cpp
//
 #include <algorithm>
 #include <vector>
 #include <iostream>
 using namespace std;

 int main ()
 {
   //
   // Initialize a vector with an array of integers.
   //
   int arr[10] = { 1,2,3,4,5,6,7,8,9,10 };
   vector<int> v(arr+0, arr+10);
   //
   // Print out elements in original (sorted) order.
   //
   cout << "Elements before reverse: " << endl << "     ";
   copy(v.begin(), v.end(),
        ostream_iterator<int,char>(cout," "));
   cout << endl << endl;
   //
   // Reverse the ordering.
   //
   reverse(v.begin(), v.end());
   //
   // Print out the reversed elements.
   //
   cout << "Elements after reverse: " << endl << "     ";
   copy(v.begin(), v.end(),
        ostream_iterator<int,char>(cout," "));
   cout << endl << endl;

   cout << "A reverse_copy to cout: " << endl << "     ";
   reverse_copy(v.begin(), v.end(), 
                ostream_iterator<int,char>(cout, " "));
   cout << 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

If your compiler does not support default template parameters, then you always need to supply the Allocator template argument. For instance, you need to write:

vector<int, allocator<int> >

instead of:

vector<int>

If your compiler does not support namespaces, then you do not need the using declaration for std.

reverse