The C++ reverse_copy function is employed to duplicate the elements from the range [first, last) to a different range that starts at result, ensuring that the elements are arranged in reverse order.
Syntax
template <class BidirectionalIterator, class OutputIterator>
OutputIterator reverse_copy (BidirectionalIterator first,
BidirectionalIterator last, OutputIterator result);
Note: BidirectionalIterator is an iterator which is used to access any elements of a container in both forward and backward direction.
Parameter
A bidirectional iterator indicates the location of the initial element within the range where the elements are being reversed.
last: A forward iterator indicating the position immediately after the last element in the range where the elements are being reversed.
The result is an output iterator that points to the starting position of the range where elements are being duplicated.
Return value
This function provides an output iterator that points to the end of the destination range [first, last), where the modified sequence of elements is being copied.
Complexity
The complexity increases linearly within the specified range [initial, final) during the process of assigning values to individual elements.
Data races
The items within the range [first, last) are being accessed.
The items within the range from the outcome to the value that is handed back are altered.
Exceptions
This function raises an exception when either an element assignment or an operation on iterator results in an exception.
Note: The invalid parameters cause an undefined behavior.
Example 1
Let's explore a basic example to showcase the functionality of reverse_copy:
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
vector<int> v({1,2,3});
cout << "Before: ";
for (const auto& value : v) {
cout << value << " ";
}
cout << '\n';
vector<int> destination(3);
reverse_copy(begin(v), end(v), begin(destination));
cout << "After: ";
for (const auto& value : destination) {
cout <<value << " ";
}
cout << '\n';
return 0;
}
Output:
Before: 1 2 3
After: 3 2 1
Example 2
Let's explore another straightforward illustration of reversing a string:
#include <algorithm>
#include <iostream>
#include <string>
#include <iterator>
using namespace std;
int main() {
string str = "Hello Myself Nikita";
cout<<"Before Reverse: "<< str<< endl;
cout<<"After Reverse: ";
reverse_copy(str.begin(), str.end(),
ostream_iterator<char>(cout, ""));
return 0;
}
Output:
Before Reverse: Hello Myself Nikita
After Reverse: atikiN flesyM olleH
Example 3
Let's explore another straightforward example of reversing a range of numbers:
#include <vector>
#include <algorithm>
#include <iostream>
int main( ) {
using namespace std;
vector <int> v1, v2( 10 );
vector <int>::iterator Iter1, Iter2;
int i;
for ( i = 0 ; i <= 9 ; i++ )
{
v1.push_back( i );
}
cout << "The original vector v1 is:\n ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;
// Reverse the elements in the vector
reverse_copy (v1.begin( ), v1.end( ), v2.begin( ) );
cout << "The copy v2 of the reversed vector v1 is:\n ( " ;
for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
cout << *Iter2 << " ";
cout << ")." << endl;
cout << "The original vector v1 remains unmodified as:\n ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;
return 0;
}
Output:
The original vector v1 is:
( 0 1 2 3 4 5 6 7 8 9 ).
The copy v2 of the reversed vector v1 is:
( 9 8 7 6 5 4 3 2 1 0 ).
The original vector v1 remains unmodified as:
( 0 1 2 3 4 5 6 7 8 9 ).
Example 4
Let's see another simple example:
#include <iostream>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <iterator>
using namespace std;
void print(string a[], int N)
{
for(int i = 0; i < N; i++)
{
cout << (i + 1) << ". " << setw(5)
<< a[i] << " ";
}
cout << endl;
}
int main()
{
string s[] = {"George", "John", "Nikki", "Alice", "Bob", "Watson"};
string t[6];
cout << "Original order : ";
print(s, 6);
cout << "\nReversing the order ... " << endl;
// Doesn't modify original array s[]
reverse_copy(s, s + 6, t);
cout << "Reversed order : ";
print(t, 6);
return 0;
}
Output:
Original order : 1. George 2. John 3. Nikki 4. Alice 5. Bob 6. Watson
Reversing the order ...
Reversed order : 1. Watson 2. Bob 3. Alice 4. Nikki 5. John 6. George
