• CodeMonkey@programming.dev
      link
      fedilink
      arrow-up
      3
      ·
      edit-2
      1 month ago

      I was a bit surprised that deque is implemented as a linked list and not, for example, a ring buffer. It would mean that index reads would be constant time (though insert and delete at an index would be linear time), the opposite of using a linked list.

      • Eager Eagle@lemmy.world
        link
        fedilink
        English
        arrow-up
        1
        ·
        1 month ago

        But a ring buffer is a FIFO data structure that can be implemented using linked lists. What ring buffer implementation did you have in mind?

          • Eager Eagle@lemmy.world
            link
            fedilink
            English
            arrow-up
            0
            arrow-down
            1
            ·
            1 month ago

            Since VecDeque is a ring buffer, its elements are not necessarily contiguous in memory.

            • FizzyOrange@programming.dev
              link
              fedilink
              arrow-up
              2
              ·
              1 month ago

              No that’s a subtly different thing. The storage is a contiguous vector, but because it is a ring buffer there must be one pair of adjacent elements that are not contiguous in memory. That’s what that comment is saying.

              But because it is only one discontinuity it doesn’t affect algorithmic complexity, so it is still O(1) to access elements, unlike a linked list which is O(N).

              If you google “circular buffer” there will be loads of diagrams that make it really obvious how it works.

        • CodeMonkey@programming.dev
          link
          fedilink
          arrow-up
          1
          ·
          1 month ago

          I am used to seeing ring buffers implemented using an array. They are FIFO if you write to the maximum offset and read from the minimum offset but they are double ended if you have a method to read from the maximum offset and write to the minimum offset.