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ArrayList vs LinkedList: Efficiency Comparison in Computer Science

This comprehensive comparison explores the efficiency differences between ArrayLists and LinkedLists. It covers key operations such as adding, sizing, and clearing elements, highlighting how ArrayLists may need resizing while LinkedLists maintain simple additions at the back. Both maintain size but clear differently. It also analyzes retrieval and setting of elements, where ArrayLists excel with O(1) operations, but LinkedLists face O(N) challenges. Lastly, we discuss additional LinkedList operations that enhance its capabilities, providing a summary of when to choose each data structure.

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ArrayList vs LinkedList: Efficiency Comparison in Computer Science

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  1. Comparison of ArrayList Efficiency to LinkedList Computer Science 4 Mr. Gerb Reference: Objective: Understand the differences between the efficiencies of LinkedLists and ArrayLists.

  2. Add, Size, Clear • Add • Adds to end of list • In ArrayList might need to resize list • In LinkedList, simply add to the back of the list (LinkedList keeps a reference to the last node) • Size: Same for ArrayLists as LinkedLists. Both keep track of the size of the list • Clear • ArrayList sets the size to 0 • LinkedList sets the front and back pointers to null. Nodes in the list are garbage-collected • Both O(1)

  3. Get and Set • Get(int n) - Get the nth item in the list • O(1) in ArrayList. Simply retrieve desired Object • Much slower in LinkedList (O(N)) • Pointers are not kept to each element in the list • Method must “count” nodes to the Nth • Set(int n, Object ob) - Set the nth item in the list • Also O(1) in ArrayList. Simply set the desired element. • Also much slower in LikedList (O(N)). Must count nodes.

  4. Remove Remove(int n) - Remove and return nth element: • O(N) in ArrayList. Must move all subsequent elements down one position. Takes an average of N/2 moves. • O(N) in Linked list: • The removal is easy (O(1), need only to change the pointers on the next and previous nodes. • But must count nodes to reach the node to be removed. • Thus remove is O(N) for both ArrayLists and LinkedLists.

  5. Comparison of efficiency of ArrayList and LinkedList

  6. Additional operations provided by LinkedList • getFirst – O(1) in both ArrayList (as get(1)) and LinkedList • getLast – O(1) in both ArrayList (as get(list.size())) and LinkedList • removeFirst – O(N) in ArrayList (as remove(1)) but O(1) in LinkedList. • removeLast – O(1) in both ArrayList (as remove(list.size())) and LinkedList • addFirst - O(1) in Linked List. Unavailable in ArrayList.

  7. Compare LinkedList’s additional operations with ArrayList

  8. Summary • Compared to ArrayLists: • LinkedList is more efficient for adding (no resizing) • LinkedList is less efficient for getting and setting a specified element. (LinkedList must count nodes). • LinkedList’s additional capabilities • All O(1) • removeFirst is more efficient than O(N) ArrayList • addFirst is unavailable in ArrayList

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