reverse

Algorithm

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Reverse the order of elements in a collection.

None

#include <algorithm>

template <class BidirectionalIterator>
void reverse (BidirectionalIterator first,
              BidirectionalIterator last);

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 <= (last - first)/2 , reverse applies swap to all pairs of iterators first + I, (last - I) - 1.

Because the iterators are assumed to be bidirectional, reverse does not return anything.

reverse performs exactly (last - first)/2 swaps.

//
// reverse.cpp
//
 #include <algorithm>
 #include <vector>
 #include <iostream.h>
 int main()
 {
   //Initialize a vector with an array of ints
   int arr[10] = {1,2,3,4,5,6,7,8,9,10};
   vector<int> v(arr, 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;

   return 0;
 }

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 need to always supply the Allocator template argument. For instance, you will need to write :

vector<int, allocator<int> >

instead of :

vector<int>

reverse_copy, swap

©Copyright 1996, Rogue Wave Software, Inc.