How do I avoid iterator invalidation with std::vector?

Iterator invalidation occurs when an operation on a container, like a std::vector, modifies its structure (e.g., resizing). This can lead to iterators pointing to invalid memory locations. To avoid iterator invalidation with std::vector, here are some strategies:

  • Reserve enough space in advance using vector::reserve() to minimize the chances of resizing.
  • Use std::vector::insert() or std::vector::emplace() to add elements, ensuring you work with iterators that remain valid.
  • Avoid operations that can rearrange the container while iterating over it, like std::vector::erase() or std::vector::push_back() during a loop.
  • Consider using other containers like std::list if you need to frequently insert or remove elements at arbitrary positions.

Here’s an example demonstrating the use of reserve() to avoid iterator invalidation:

std::vector v; v.reserve(10); // Reserve space for 10 elements for (int i = 0; i < 10; ++i) { v.push_back(i); } auto it = v.begin(); while (it != v.end()) { std::cout << *it << " "; ++it; }

std::vector iterator invalidation C++ avoid iterator invalidation container operations

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