2. Linear Queue using Linked List

In [1]:

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

    def __repr__(self):
        return "<Node: %s>" % s

class Node: def __init__(self, data): self.data = data self.next = None def __repr__(self): return "" % s

In [2]:

class Queue:
    def __init__(self, max_size):
        self.front = None
        self.rear = None
        self.count = 0
        self.capacity = max_size

    def __iter__(self):
        ptr = self.front
        while ptr is not None:
            yield ptr.data
            ptr = ptr.next

    def __repr__(self):
        temp = self.front
        nodes = []
        while temp:
            if temp == self.front:
                nodes.append("[Front: %s]" % temp.data)
            elif temp == self.rear:
                nodes.append("[Rear: %s]" % temp.data)
            else:
                nodes.append("[%s]" % temp.data)
            temp = temp.next
        return "<-".join(nodes)

    def __len__(self):
        return self.count

    def peek(self):
        if self.front is not None:
            return self.front.data

    def enqueue(self, data):
        if self.count == self.capacity:
            print("queue is full, dequeue all elements first")
            return

        node = Node(data)
        if self.front == self.rear == None:
            print("inserting first element in queue")
            self.front = self.rear = node
        else:
            print(f"Inserting: {data} in the queue")
            self.rear.next = node
            self.rear = self.rear.next
        self.count += 1

    def dequeue(self):
        if self.count == 0:
            print("Queue is empty")
            self.front = self.rear = None
        elif self.front is not None:
            data = self.front.data
            print(f"Removing: {data} from the queue")
            temp = self.front
            self.front = self.front.next
            del temp
            self.count -= 1

class Queue: def __init__(self, max_size): self.front = None self.rear = None self.count = 0 self.capacity = max_size def __iter__(self): ptr = self.front while ptr is not None: yield ptr.data ptr = ptr.next def __repr__(self): temp = self.front nodes = [] while temp: if temp == self.front: nodes.append("[Front: %s]" % temp.data) elif temp == self.rear: nodes.append("[Rear: %s]" % temp.data) else: nodes.append("[%s]" % temp.data) temp = temp.next return "<-".join(nodes) def __len__(self): return self.count def peek(self): if self.front is not None: return self.front.data def enqueue(self, data): if self.count == self.capacity: print("queue is full, dequeue all elements first") return node = Node(data) if self.front == self.rear == None: print("inserting first element in queue") self.front = self.rear = node else: print(f"Inserting: {data} in the queue") self.rear.next = node self.rear = self.rear.next self.count += 1 def dequeue(self): if self.count == 0: print("Queue is empty") self.front = self.rear = None elif self.front is not None: data = self.front.data print(f"Removing: {data} from the queue") temp = self.front self.front = self.front.next del temp self.count -= 1

In [3]:

queue = Queue(5)

queue = Queue(5)

In [4]:

queue

queue

Out[4]:

In [5]:

for i in range(10):
    queue.enqueue(i)

for i in range(10): queue.enqueue(i)

inserting first element in queue
Inserting: 1 in the queue
Inserting: 2 in the queue
Inserting: 3 in the queue
Inserting: 4 in the queue
queue is full, dequeue all elements first
queue is full, dequeue all elements first
queue is full, dequeue all elements first
queue is full, dequeue all elements first
queue is full, dequeue all elements first

In [6]:

for i in queue:
    print(i)

for i in queue: print(i)

0
1
2
3
4

In [7]:

queue

queue

Out[7]:

[Front: 0]<-[1]<-[2]<-[3]<-[Rear: 4]

In [8]:

queue.dequeue()

queue.dequeue()

Removing: 0 from the queue

In [9]:

queue

queue

Out[9]:

[Front: 1]<-[2]<-[3]<-[Rear: 4]

In [10]:

for _ in range(10):
    queue.dequeue()

for _ in range(10): queue.dequeue()

Removing: 1 from the queue
Removing: 2 from the queue
Removing: 3 from the queue
Removing: 4 from the queue
Queue is empty
Queue is empty
Queue is empty
Queue is empty
Queue is empty
Queue is empty

In [11]:

queue

queue

Out[11]:

In [12]:

for i in range(10):
    queue.enqueue(i)

for i in range(10): queue.enqueue(i)

inserting first element in queue
Inserting: 1 in the queue
Inserting: 2 in the queue
Inserting: 3 in the queue
Inserting: 4 in the queue
queue is full, dequeue all elements first
queue is full, dequeue all elements first
queue is full, dequeue all elements first
queue is full, dequeue all elements first
queue is full, dequeue all elements first

In [13]:

queue

queue

Out[13]:

[Front: 0]<-[1]<-[2]<-[3]<-[Rear: 4]

In [14]:

len(queue)

len(queue)

Out[14]:

5

In [15]:

queue.peek()

queue.peek()

Out[15]:

0

In [16]:

queue.dequeue()

queue.dequeue()

Removing: 0 from the queue

In [17]:

queue.peek()

queue.peek()

Out[17]:

1

In [ ]: