Python data structures and algorithms--queues

The queue structure can be modeled using an array, with only two markers for the head and tail to be set

Reference from "Aha"

1 #The code in the book will be indexed out of bounds (the book has applied for excessive space)2 #try to initialize the Tai to Len (q)-1 without error but with the last one missing3 #by exception handling, capturing out-of-bounds exceptions jumps directly out of the loop4 defQueue_demo1 (q):5Newq = []6Head =07tail = len (q)#record queue last one8     9      whileHead <Tail:Ten newq.append (Q[head]) OneHead + 1 A         Try: - q.append (Q[head]) -         exceptIndexerror: the              Break                    -Head + 1 -Tail + = 1 -          +     returnNewq

The use of specific methods and considerations, the following different ways of implementation is the same truth:

if __name__=="__main__":#Note that inserting inserts and deleting del operations outside of the list tail is time-consuming#best to use only append or extendQ= List ("631758924")#separating string sequencesNewq =Queue_demo (q)PrintNewq>>> ['6','1','5','9','4','7','2','8','3']

We can also implement the queue type ourselves:

1 #======= Manually implementing the queue type =======2 #Queue node Element3 classNode:4     def __init__(self,data,next=None):5Self.data =Data6Self.next =Next7 8 #simple FIFO queue category9 classQueue:Ten     def __init__(self): OneSelf.head =None ASelf.tail =None -Self.count =0 -          the     defAppend (self,data): -         ifSelf.head = =None: -Self.head =Node (data) -Self.tail =Self.head +         Else: -Self.tail.next =Node (data) +Self.tail =Self.tail.next ASelf.count + = 1 at      -     defpop (self): -         ifSelf.head = =None: -             Raise "Error:head==none" -data =Self.head.data -Self.head =Self.head.next inSelf.count-= 1 -         returnData to  + #new implementation of the above algorithm - defQueue_demo2 (q): the      *Queue =Queue () $      forIteminchQ:#Initialize QueuePanax Notoginseng queue.append (item) -  theNewq = [] +      whileQueue.count >0: ANewq.append (Queue.pop ())#record the deleted element the         ifqueue.count==0: +              Break -         Else: $temp = Queue.pop ()#elements from the new queue $ queue.append (temp) -      -     returnNewq

Python provides a built-in data structure in the collections module

#using Python built-in objects#deque: Double-ended queue that can quickly append and insert objects from both sides#Note that list.pop (0) can also pop up the first element, but it's actually time-consuming.defQueue_demo3 (q): fromCollectionsImportdeque#good, suddenly found that their own method of writing and built-in object name exactly the same, the code does not have to change    #I also guess the above ...Queue =deque () forIteminchQ:#Initialize Queuequeue.append (item) NEWQ= []     whileQueue.count >0:newq.append (Queue.pop ())#record the deleted element        ifqueue.count==0: Break        Else: Temp= Queue.pop ()#elements from the new queuequeue.append (temp)returnNewq

Python data structures and algorithms--queues