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In computer science, a priority queue is an abstract data type which is like a regular queue or stack data structure, but where additionally each element has a "priority" associated with it. In a priority queue, an element with high priority is served before an element with low priority. If two elements have the same priority, they are served according to their order in the queue. While priority queues are often implemented with heaps, they are conceptually distinct from heaps. A priority queue is an abstract concept like "a list" or "a map"; just as a list can be implemented with a linked list or an array, a priority queue can be implemented with a heap or a variety of other methods such as an unordered array. == Operations == A priority queue must at least support the following operations: * ''insert_with_priority'': add an element to the queue with an associated priority. * ''pull_highest_priority_element'': remove the element from the queue that has the ''highest priority'', and return it. *: This is also known as "''pop_element(Off)''", "''get_maximum_element''" or "''get_front(most)_element''". *: Some conventions reverse the order of priorities, considering lower values to be higher priority, so this may also be known as "''get_minimum_element''", and is often referred to as "''get-min''" in the literature. *: This may instead be specified as separate "''peek_at_highest_priority_element''" and "''delete_element''" functions, which can be combined to produce "''pull_highest_priority_element''". In addition, ''peek'' (in this context often called ''find-max'' or ''find-min''), which returns the highest-priority element but does not modify the queue, is very frequently implemented, and nearly always executes in ''O''(1) time. This operation and its ''O''(1) performance is crucial to many applications of priority queues. More advanced implementations may support more complicated operations, such as ''pull_lowest_priority_element'', inspecting the first few highest- or lowest-priority elements, clearing the queue, clearing subsets of the queue, performing a batch insert, merging two or more queues into one, incrementing priority of any element, etc. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Priority queue」の詳細全文を読む スポンサード リンク
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