Copying Algorithms

# Handling Overlapping Ranges when Copying

## How can I handle copying objects when the source and destination ranges overlap in complex ways?

Handling overlapping ranges can be tricky because the default behavior of std::ranges::copy() and std::ranges::copy_backward() assumes non-overlappingÂ ranges.

When the ranges overlap, you need to be careful to avoid undefinedÂ behavior.

If the destination is to the right of the source within the same container, you should use std::ranges::copy_backward() instead of std::ranges::copy().

This ensures that elements are copied from the end of the range to the beginning, preserving the order of elements. Hereâ€™s anÂ example:

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

int main() {
std::vector<int> Values{1, 2, 3, 0, 0};

std::ranges::copy_backward(
Values.begin(), Values.begin() + 3,
Values.end());

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

In this example, using std::ranges::copy_backward() ensures that elements are copied correctly even though the destination overlaps with theÂ source.

If the destination is to the left of the source, you can safely use std::ranges::copy(). Hereâ€™s anÂ example:

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

int main() {
std::vector<int> Values{0, 0, 1, 2, 3};

std::ranges::copy(
Values.begin() + 2, Values.end(),
Values.begin());

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

In this case, std::ranges::copy() works correctly because the destination is to the left of the sourceÂ range.

When dealing with more complex overlaps, you might need to divide the range into non-overlapping sub-ranges and handle each one appropriately. Always ensure that you understand the layout of your source and destination ranges to choose the correctÂ algorithm.

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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