[edu] queue (with node)

단방향 linked list 를 이용해서

queue 를 구현해 보자

매직 키워드를 사용해서 for, enumerate, len, slicing, 등등 기능도 구현해 보자

class Node:
    def __init__(self, data, next=None):
        self.data, self.next = data, next


class Queue:
    def __init__(self):
        self.head = None
        self.size = 0

    def is_empty(self): return not bool(self.size)

    def enqueue(self, data):
        if self.is_empty():
            self.head = Node(data)
        else:
            cur_node = self.head
            while cur_node.next:
                cur_node = cur_node.next
            cur_node.next = Node(data)
        self.size += 1

    def dequeue(self):
        if self.is_empty():
            return None
        ret_data, self.head = self.head.data, self.head.next
        self.size -= 1
        return ret_data

    def peek(self): return None if self.is_empty() else self.head.data

    def __getitem__(self, index):
        cur_node = self.head
        for _ in range(index):
            cur_node = cur_node.next
        return cur_node.data

    def __iter__(self):
        return (item for item in range(len(self)))

    def __len__(self):
        return self.size


q = Queue()
print(q.is_empty())
# enqueue
for i in range(10):
    q.enqueue(i*i)
# enumerate
for i, v in enumerate(q):
    print(i, v)
# peek (first in first out)
print(q.peek())
# dequeue
while not q.is_empty():
    print(q.dequeue())

print(q.is_empty())
# enumerate
for i, v in enumerate(q):
    print(i, v)