Deque (Doubly Ended Queue) v Pythonu je implementiran z uporabo modula zbirke . Deque ima prednost pred seznamom v primerih, ko potrebujemo hitrejše operacije dodajanja in izpiranja z obeh koncev vsebnika, saj deque zagotavlja O(1) časovna zapletenost za operacije dodajanja in izpiranja v primerjavi s seznamom, ki zagotavlja O(n) časovno zapletenost.
Vrste omejenega vnosa deque
- Input Restricted Deque : Vnos je omejen na enem koncu, medtem ko je brisanje dovoljeno na obeh koncih. Output Restricted Deque: izhod je omejen na enem koncu, vstavljanje pa je dovoljeno na obeh koncih.
Primer: koda Python za predstavitev
Python3
from> collections>import> deque> > # Declaring deque> queue>=> deque([>'name'>,>'age'>,>'DOB'>])> > print>(queue)> |
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>Izhod
deque(['name', 'age', 'DOB'])>
Operacije na deque
Primer 1: Učinkovito dodajanje elementov
- append() :- Ta funkcija se uporablja za vstavljanje vrednosti v njen argument na desni konec deque. appendleft() :- Ta funkcija se uporablja za vstavljanje vrednosti v njen argument na levi konec deque.
Python3
vrzi obravnavanje izjem v Javi
# importing 'collections' for deque operations> import> collections> # initializing deque> de>=> collections.deque([>1>,>2>,>3>])> print>(>'deque: '>, de)> # using append() to insert element at right end> # inserts 4 at the end of deque> de.append(>4>)> # printing modified deque> print>(>'
The deque after appending at right is : '>)> print>(de)> # using appendleft() to insert element at left end> # inserts 6 at the beginning of deque> de.appendleft(>6>)> # printing modified deque> print>(>'
The deque after appending at left is : '>)> print>(de)> |
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>Izhod
deque: deque([1, 2, 3]) The deque after appending at right is : deque([1, 2, 3, 4]) The deque after appending at left is : deque([6, 1, 2, 3, 4])>
Napotite se na konec za analizo kompleksnosti.
Primer 2: Učinkovito pokanje predmetov
- pop() :- Ta funkcija se uporablja za brisanje argumenta z desnega konca deque. popleft() :- Ta funkcija se uporablja za brisanje argumenta z levega konca deque.
Python3
# importing 'collections' for deque operations> import> collections> # initializing deque> de>=> collections.deque([>6>,>1>,>2>,>3>,>4>])> print>(>'deque: '>, de)> # using pop() to delete element from right end> # deletes 4 from the right end of deque> de.pop()> # printing modified deque> print>(>'
The deque after deleting from right is : '>)> print>(de)> # using popleft() to delete element from left end> # deletes 6 from the left end of deque> de.popleft()> # printing modified deque> print>(>'
The deque after deleting from left is : '>)> print>(de)> |
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>Izhod
deque: deque([6, 1, 2, 3, 4]) The deque after deleting from right is : deque([6, 1, 2, 3]) The deque after deleting from left is : deque([1, 2, 3])>
Napotite se na konec za analizo kompleksnosti.
Primer 3: Dostopanje do elementov v deque
- index(ele, beg, end) :- Ta funkcija vrne prvi indeks vrednosti, omenjene v argumentih, z začetkom iskanja od začetnega do končnega indeksa. vstavi (i, a) :- Ta funkcija vstavi vrednost, omenjeno v argumentih (a), v indeks (i), podanem v argumentih. remove() :- Ta funkcija odstrani prvo pojavitev vrednosti, omenjene v argumentih. count() :- Ta funkcija prešteje število pojavitev vrednosti, omenjene v argumentih.
Python3
# Python code to demonstrate working of> # insert(), index(), remove(), count()> # importing 'collections' for deque operations> import> collections> # initializing deque> de>=> collections.deque([>1>,>2>,>3>,>3>,>4>,>2>,>4>])> # using index() to print the first occurrence of 4> print> (>'The number 4 first occurs at a position : '>)> print> (de.index(>4>,>2>,>5>))> # using insert() to insert the value 3 at 5th position> de.insert(>4>,>3>)> # printing modified deque> print> (>'The deque after inserting 3 at 5th position is : '>)> print> (de)> # using count() to count the occurrences of 3> print> (>'The count of 3 in deque is : '>)> print> (de.count(>3>))> # using remove() to remove the first occurrence of 3> de.remove(>3>)> # printing modified deque> print> (>'The deque after deleting first occurrence of 3 is : '>)> print> (de)> |
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>Izhod
The number 4 first occurs at a position : 4 The deque after inserting 3 at 5th position is : deque([1, 2, 3, 3, 3, 4, 2, 4]) The count of 3 in deque is : 3 The deque after deleting first occurrence of 3 is : deque([1, 2, 3, 3, 4, 2, 4])>
Napotite se na konec za analizo kompleksnosti.
Primer 4: Velikost deque
- len(dequeue) :- Vrne trenutno velikost dequeue.
Python3
# Python Program to demonstrate> # how to find size of a Dequeue> from> collections>import> deque> # initializing deque> de>=> deque([>1>,>2>,>3>,>4>,>5>,>6>])> print>(>'Current Deque: '>, de)> # printing current size of deque> print>(f>'Size of Deque: {len(de)}'>)> # using pop() to delete element from right end> # deletes 6 from the right end of deque> de.pop()> # printing modified deque> print>(>'
The deque after deleting from right is: '>, end>=> '')> print>(de)> # printing current size of deque> print>(f>'Size of Deque: {len(de)}'>)> # This code is contributed by Susobhan Akhuli> |
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>Izhod
Current Deque: deque([1, 2, 3, 4, 5, 6]) Size of Deque: 6 The deque after deleting from right is: deque([1, 2, 3, 4, 5]) Size of Deque: 5>
Napotite se na konec za analizo kompleksnosti.
Primer 5: Sprednja in zadnja stran deke
- Deque[0] : - Do sprednjega elementa deque lahko dostopamo z uporabo indeksiranja z de[0]. Deque[-1] :- Do zadnjega elementa deque lahko dostopamo z uporabo indeksiranja z de[-1].
Python3
# Python Program to demonstrate> # accessing the front and back of a Deque> from> collections>import> deque> # initializing deque> de>=> deque([>1>,>2>,>3>,>4>,>5>,>6>])> print>(>'Current Deque: '>, de)> # Accessing the front element of the deque> print>(>'Front element of the deque:'>, de[>0>])> # Accessing the back element of the deque> print>(>'Back element of the deque:'>, de[>->1>])> # This code is contributed by Susobhan Akhuli> |
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>Izhod
Current Deque: deque([1, 2, 3, 4, 5, 6]) Front element of the deque: 1 Back element of the deque: 6>
Napotite se na konec za analizo kompleksnosti.
Primer 6: Različne operacije na deque
- extend(iterable) :- Ta funkcija se uporablja za dodajanje več vrednosti na desni konec deque. Podan argument je ponovljiv. extendleft(iterable) :- Ta funkcija se uporablja za dodajanje več vrednosti na levi konec deque. Podan argument je ponovljiv. Vrstni red je obrnjen zaradi levih dodatkov. reverse() :- Ta funkcija se uporablja za obračanje vrstnega reda elementov deque. rotate() :- Ta funkcija zavrti deque za število, podano v argumentih. Če je navedeno število negativno, pride do rotacije v levo. Drugače je vrtenje v desno.
Python3
# Python code to demonstrate working of> # extend(), extendleft(), rotate(), reverse()> # importing 'collections' for deque operations> import> collections> # initializing deque> de>=> collections.deque([>1>,>2>,>3>,])> # using extend() to add numbers to right end> # adds 4,5,6 to right end> de.extend([>4>,>5>,>6>])> # printing modified deque> print> (>'The deque after extending deque at end is : '>)> print> (de)> # using extendleft() to add numbers to left end> # adds 7,8,9 to left end> de.extendleft([>7>,>8>,>9>])> # printing modified deque> print> (>'The deque after extending deque at beginning is : '>)> print> (de)> # using rotate() to rotate the deque> # rotates by 3 to left> de.rotate(>->3>)> # printing modified deque> print> (>'The deque after rotating deque is : '>)> print> (de)> # using reverse() to reverse the deque> de.reverse()> # printing modified deque> print> (>'The deque after reversing deque is : '>)> print> (de)> |
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>Izhod
The deque after extending deque at end is : deque([1, 2, 3, 4, 5, 6]) The deque after extending deque at beginning is : deque([9, 8, 7, 1, 2, 3, 4, 5, 6]) The deque after rotating deque is : deque([1, 2, 3, 4, 5, 6, 9, 8, 7]) The deque after reversing deque is : deque([7, 8, 9, 6, 5, 4, 3, 2, 1])>
Napotite se na konec za analizo kompleksnosti.
Analiza kompleksnosti:
| Metode | Časovna zapletenost | Pomožni prostor |
|---|---|---|
| pripni() | O(1) | O(1) |
| pripni levo() | O(1) | O(1) |
| pop() | O(1) | O(1) |
| popleft() | O(1) | O(1) |
| indeks(ele, začetek, konec) | O(N) | O(1) |
| vstavi (i, a) | O(N) | O(1) |
| Odstrani() | O(N) | O(1) |
| štetje () | O(N) | O(1) |
| samo (iz vrste) | O(1) | O(1) |
| Deque[0] | O(1) | O(1) |
| Deque[-1] | O(1) | O(1) |
| podaljšati (iterable) | PUŠČICA) | O(1) |
| podaljšano levo (ponovljivo) | PUŠČICA) | O(1) |
| obratno() | O(N) | O(1) niz v c |
| vrti() | PUŠČICA) | O(1) |