Problem Statement
Explain the differences between arrays and linked lists. When would you choose one over the other?
Explanation
Arrays and linked lists are both linear data structures, but they differ fundamentally in how they store and access elements.
Arrays store elements in contiguous memory locations, allowing direct access to any element using its index in O of 1 time. The size is fixed at creation, making insertion and deletion expensive operations requiring shifting of elements, with time complexity of O of n. Arrays use less memory per element as they only store data, and they provide better cache locality due to contiguous storage.
Linked lists store elements as nodes scattered in memory, with each node containing data and a pointer to the next node. Access to elements requires traversal from the head, taking O of n time. The size is dynamic and can grow or shrink as needed. Insertion and deletion are efficient at O of 1 if you have a reference to the position, requiring only pointer updates. However, linked lists use more memory per element due to storing pointers, and they have poor cache locality.
Choose arrays when you need fast random access by index, when the size is known beforehand and does not change frequently, when memory efficiency is critical as arrays have less overhead, and when you need to perform many read operations compared to insertions and deletions. Arrays are ideal for implementing other data structures like heaps and hash tables, and for scenarios requiring sorted data with binary search.
Choose linked lists when the size is unknown or changes frequently, when you need frequent insertions and deletions especially at the beginning or middle, when you do not need random access to elements, and when implementing data structures like stacks, queues, and graphs. Linked lists are better when memory is fragmented and contiguous allocation is difficult.
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