Re: Реверс.

From

Dmitriy Gerasimenko ()

To

Ruslan Teluk

Date

2002-08-12T14:59:49Z

Area

RU.ALGORITHMS

From: "Dmitriy Gerasimenko" <gerasimenko@karelia.ru>


RT> Есть ли алгоритмы для быстрого реверса массива?

С++ библиотека STL
файл - #include <algorithm>..:)
//--------------------------------------------------------------------------
Summary

Reverses the order of elements in a collection.

Synopsis

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

Description

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.

Complexity

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

Example

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

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

Warnings

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.

See Also

reverse_copy, swap
//--------------------------------------------------------------------------
-


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