Copying Algorithms

# Copying with Different Ordering

## Is it possible to copy elements from a range to a destination with a different ordering, not just reversed or rotated?

Yes, it is possible to copy elements from a range to a destination with a different ordering, not just reversed orÂ rotated.

You can achieve this by using custom sorting or shuffling algorithms before or during the copyÂ process.

### Custom Sorting Before Copy

One approach is to sort the elements in the desired order before copying them to the destination container. Hereâ€™s anÂ example:

#include <algorithm>
#include <iostream>
#include <vector>

int main() {
std::vector<int> Source{5, 3, 1, 4, 2};
std::vector<int> Destination(5);

// Sort the source range in ascending order
std::sort(Source.begin(), Source.end());

// Copy the sorted range to the destination
std::ranges::copy(Source, Destination.begin());

for (int Value : Destination) {
std::cout << Value << ", ";
}
}
1, 2, 3, 4, 5,

### Custom Order During Copy

Another approach is to define a custom order during the copy process using a permutation or a customÂ transformation.

### Using a Permutation Index

You can use an index array to define a custom order and apply this order during the copyÂ process:

#include <algorithm>
#include <iostream>
#include <vector>

int main() {
std::vector<int> Source{10, 20, 30, 40, 50};
std::vector<int> Destination(5);
std::vector<size_t> Permutation{4, 2, 0, 3, 1};

for (size_t i = 0; i < Source.size(); ++i) {
Destination[i] = Source[Permutation[i]];
}

for (int Value : Destination) {
std::cout << Value << ", ";
}
}
50, 30, 10, 40, 20,

### Using Transform Iterator

For more complex transformations, you can use a transform iterator to apply a function to each element during theÂ copy:

#include <algorithm>
#include <iostream>
#include <vector>
#include <iterator>

int main() {
std::vector<int> Source{1, 2, 3, 4, 5};
std::vector<int> Destination(5);

std::transform(Source.begin(), Source.end(),
Destination.begin(),
[](int x) { return x * x; });

for (int Value : Destination) {
std::cout << Value << ", ";
}
}
1, 4, 9, 16, 25,

### Using Custom Comparison

You can also use a custom comparison function to define a specific order and then copy theÂ elements:

#include <algorithm>
#include <iostream>
#include <vector>

bool customCompare(int a, int b) {
// Group even and odd numbers
return (a % 2) < (b % 2);
}

int main() {
std::vector<int> Source{1, 2, 3, 4, 5};
std::vector<int> Destination(5);

std::sort(Source.begin(), Source.end(),
customCompare);

std::ranges::copy(Source, Destination.begin());

for (int Value : Destination) {
std::cout << Value << ", ";
}
}
2, 4, 1, 3, 5,

By using these techniques, you can copy elements in a custom order that suits your specificÂ requirements.

This Question is from the Lesson:

### Copying Algorithms

An introduction to the 7 copying algorithms in the C++ standard library: copy(), copy_n(), copy_if(), copy_backward(), reverse_copy(), rotate_copy(), and unique_copy().

Answers to questions are automatically generated and may not have been reviewed.

This Question is from the Lesson:

### Copying Algorithms

An introduction to the 7 copying algorithms in the C++ standard library: copy(), copy_n(), copy_if(), copy_backward(), reverse_copy(), rotate_copy(), and unique_copy().

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