reverse(3C++)

Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

NAME

reverse

- 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.

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