![]() ![]() One of LISP's major data structures is the linked list.īy the early 1960s, the utility of both linked lists and languages which use these structures as their primary data representation was well established. LISP, standing for list processor, was created by John McCarthy in 1958 while he was at MIT and in 1960 he published its design in a paper in the Communications of the ACM, entitled "Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I". Īnother early appearance of linked lists was by Hans Peter Luhn who wrote an internal IBM memorandum in January 1953 that suggested the use of linked lists in chained hash tables. A report on this language entitled "A programming language for mechanical translation" appeared in Mechanical Translation in 1958. The problem of machine translation for natural language processing led Victor Yngve at Massachusetts Institute of Technology (MIT) to use linked lists as data structures in his COMIT programming language for computer research in the field of linguistics. Newell and Simon were recognized with the ACM Turing Award in 1975 for having "made basic contributions to artificial intelligence, the psychology of human cognition, and list processing". The now-classic diagram consisting of blocks representing list nodes with arrows pointing to successive list nodes appears in "Programming the Logic Theory Machine" by Newell and Shaw in Proc. Reports on their work appeared in IRE Transactions on Information Theory in 1956, and several conference proceedings from 1957 to 1959, including Proceedings of the Western Joint Computer Conference in 19, and Information Processing (Proceedings of the first UNESCO International Conference on Information Processing) in 1959. IPL was used by the authors to develop several early artificial intelligence programs, including the Logic Theory Machine, the General Problem Solver, and a computer chess program. Simon at RAND Corporation as the primary data structure for their Information Processing Language. Linked lists were developed in 1955–1956, by Allen Newell, Cliff Shaw and Herbert A. 6.1 Example of internal and external storage.On the other hand, since simple linked lists by themselves do not allow random access to the data or any form of efficient indexing, many basic operations-such as obtaining the last node of the list, finding a node that contains a given datum, or locating the place where a new node should be inserted-may require iterating through most or all of the list elements. ![]() Linked lists allow insertion and removal of nodes at any point in the list, and allow doing so with a constant number of operations by keeping the link previous to the link being added or removed in memory during list traversal. The principal benefit of a linked list over a conventional array is that the list elements can be easily inserted or removed without reallocation or reorganization of the entire structure because the data items need not be stored contiguously in memory or on disk, while restructuring an array at run-time is a much more expensive operation. They can be used to implement several other common abstract data types, including lists, stacks, queues, associative arrays, and S-expressions, though it is not uncommon to implement those data structures directly without using a linked list as the basis. ![]() Linked lists are among the simplest and most common data structures. Arrays have better cache locality compared to linked lists. Faster access, such as random access, is not feasible. A drawback of linked lists is that access time is linear (and difficult to pipeline). More complex variants add additional links, allowing more efficient insertion or removal of nodes at arbitrary positions. This structure allows for efficient insertion or removal of elements from any position in the sequence during iteration. In its most basic form, each node contains: data, and a reference (in other words, a link) to the next node in the sequence. It is a data structure consisting of a collection of nodes which together represent a sequence. Instead, each element points to the next. In computer science, a linked list is a linear collection of data elements whose order is not given by their physical placement in memory. The last node is linked to a terminator used to signify the end of the list. A linked list is a sequence of nodes that contain two fields: an integer value and a link to the next node. ![]()
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