[Python 자료구조] 큐 (Queues)

(Representation of a  FIFO  (first in, first out) queue, Wikipedia)

#연산의 정의

• size() : 현재 큐에 들어있는 데이터 원소의 수를 구함
• isEmpty() : 현재 큐가 비어 있는지를 판단
• enqueue(x) : 데이터 원소 x를 큐에 추가
• dequeue() : 큐의 맨 앞에 저장된 데이터 원소를 제거(또는 반환)
• peek() : 큐의 맨 앞에 저장된 데이터 원소를 반환(제거하지 않음)

 

#배열을 이용하여 구현

class ArrayQueue:
    def __init__(self):
        self.data = []
        
    def size(self):
        return len(self.data)

    def isEmpty(self):
        return self.size() == 0
    
    def enqueue(self, item):
        self.data.append(item)
        
    def dequeue(self):
        return self.data.pop(0)
    
    def peek(self):
        return self.data[0]

 

연산	복잡도
size()	O(1)
isEmpty()	O(1)
enqueue()	O(1)
dequeue()	O(n)
peek()	O(1)

 

 

#이중 연결리스트을 이용하여 구현

class Node:

    def __init__(self, item):
        self.data = item
        self.prev = None
        self.next = None

class DoublyLinkedList:

    def __init__(self):
        self.nodeCount = 0
        self.head = Node(None)
        self.tail = Node(None)
        self.head.prev = None
        self.head.next = self.tail
        self.tail.prev = self.head
        self.tail.next = None

    def __repr__(self):
        if self.nodeCount == 0:
            return 'LinkedList: empty'

        s = ''
        curr = self.head
        while curr.next.next:
            curr = curr.next
            s += repr(curr.data)
            if curr.next.next is not None:
                s += ' -> '
        return s

    def getLength(self):
        return self.nodeCount

    def traverse(self):
        result = []
        curr = self.head
        while curr.next.next:
            curr = curr.next
            result.append(curr.data)
        return result

    def reverse(self):
        result = []
        curr = self.tail
        while curr.prev.prev:
            curr = curr.prev
            result.append(curr.data)
        return result

    def getAt(self, pos):
        if pos < 0 or pos > self.nodeCount:
            return None

        if pos > self.nodeCount // 2:
            i = 0
            curr = self.tail
            while i < self.nodeCount - pos + 1:
                curr = curr.prev
                i += 1
        else:
            i = 0
            curr = self.head
            while i < pos:
                curr = curr.next
                i += 1

        return curr

    def insertAfter(self, prev, newNode):
        next = prev.next
        newNode.prev = prev
        newNode.next = next
        prev.next = newNode
        next.prev = newNode
        self.nodeCount += 1
        return True

    def insertAt(self, pos, newNode):
        if pos < 1 or pos > self.nodeCount + 1:
            return False

        prev = self.getAt(pos - 1)
        return self.insertAfter(prev, newNode)

    def popAfter(self, prev):
        curr = prev.next
        next = curr.next
        prev.next = next
        next.prev = prev
        self.nodeCount -= 1
        return curr.data

    def popAt(self, pos):
        if pos < 1 or pos > self.nodeCount:
            raise IndexError('Index out of range')

        prev = self.getAt(pos - 1)
        return self.popAfter(prev)

    def concat(self, L):
        self.tail.prev.next = L.head.next
        L.head.next.prev = self.tail.prev
        self.tail = L.tail

        self.nodeCount += L.nodeCount

class LinkedListQueue:

    def __init__(self):
        self.data = DoublyLinkedList()

    def size(self):
        return self.data.nodeCount

    def isEmpty(self):
        return self.data.nodeCount==0

    def enqueue(self, item):
        node = Node(item)
        self.data.insertAt(self.size()+1,node)

    def dequeue(self):
        return self.data.popAt(1)

    def peek(self):
        return self.data.head.next.data

def solution(x):
    return 0

 

#양방향 연결리스트을 이용한 큐 구현 예제

class Node:

    def __init__(self, item):
        self.data = item
        self.prev = None
        self.next = None

class DoublyLinkedList:

    def __init__(self):
        self.nodeCount = 0
        self.head = Node(None)
        self.tail = Node(None)
        self.head.prev = None
        self.head.next = self.tail
        self.tail.prev = self.head
        self.tail.next = None

    def __repr__(self):
        if self.nodeCount == 0:
            return 'LinkedList: empty'

        s = ''
        curr = self.head
        while curr.next.next:
            curr = curr.next
            s += repr(curr.data)
            if curr.next.next is not None:
                s += ' -> '
        return s

    def getLength(self):
        return self.nodeCount

    def traverse(self):
        result = []
        curr = self.head
        while curr.next.next:
            curr = curr.next
            result.append(curr.data)
        return result

    def reverse(self):
        result = []
        curr = self.tail
        while curr.prev.prev:
            curr = curr.prev
            result.append(curr.data)
        return result

    def getAt(self, pos):
        if pos < 0 or pos > self.nodeCount:
            return None

        if pos > self.nodeCount // 2:
            i = 0
            curr = self.tail
            while i < self.nodeCount - pos + 1:
                curr = curr.prev
                i += 1
        else:
            i = 0
            curr = self.head
            while i < pos:
                curr = curr.next
                i += 1

        return curr

    def insertAfter(self, prev, newNode):
        next = prev.next
        newNode.prev = prev
        newNode.next = next
        prev.next = newNode
        next.prev = newNode
        self.nodeCount += 1
        return True

    def insertAt(self, pos, newNode):
        if pos < 1 or pos > self.nodeCount + 1:
            return False

        prev = self.getAt(pos - 1)
        return self.insertAfter(prev, newNode)

    def popAfter(self, prev):
        curr = prev.next
        next = curr.next
        prev.next = next
        next.prev = prev
        self.nodeCount -= 1
        return curr.data

    def popAt(self, pos):
        if pos < 1 or pos > self.nodeCount:
            raise IndexError('Index out of range')

        prev = self.getAt(pos - 1)
        return self.popAfter(prev)

    def concat(self, L):
        self.tail.prev.next = L.head.next
        L.head.next.prev = self.tail.prev
        self.tail = L.tail

        self.nodeCount += L.nodeCount

class LinkedListQueue:

    def __init__(self):
        self.data = DoublyLinkedList()

    def size(self):
        return self.data.nodeCount

    def isEmpty(self):
        return self.data.nodeCount==0

    def enqueue(self, item):
        node = Node(item)
        self.data.insertAt(self.size()+1,node)

    def dequeue(self):
        return self.data.popAt(1)

    def peek(self):
        return self.data.head.next.data

def solution(x):
    return 0

(솔루션 출처)

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