Deque

Author: codehariom

Queues /QueuesLinked.py

@@ -0,0 +1,79 @@
+class _Node:
+    __slots__ = '_element', '_next'
+
+    def __init__(self, element, next):
+        self._element = element
+        self._next = next
+
+class QueuesLinked:
+    def __init__(self):
+        self._front = None
+        self._rear = None
+        self._size = 0
+
+    def __len__(self):
+        return self._size
+
+    def isempty(self):
+        return self._size == 0
+
+    def enqueue(self, e):
+        newest = _Node(e, None)
+        if self.isempty():
+            self._front = newest
+        else:
+            self._rear._next = newest
+        self._rear = newest
+        self._size += 1
+
+    def dequeue(self):
+        if self.isempty():
+            print('Queue is empty')
+            return
+        e = self._front._element
+        self._front = self._front._next
+        self._size -= 1
+        if self.isempty():
+            self._rear = None
+        return e
+
+    def first(self):
+        if self.isempty():
+            print('Queue is empty')
+            return
+        return self._front._element
+
+    def display(self):
+        p = self._front
+        while p:
+            print(p._element,end=' <-- ')
+            p = p._next
+        print()
+
+
+Q = QueuesLinked()
+Q.enqueue(5)
+Q.enqueue(3)
+print('Queue:')
+Q.display()
+print('Queue Length:', len(Q))
+ele = Q.dequeue()
+print('Queue:')
+Q.display()
+print('Queue Length:', len(Q))
+print('Removed Element:',ele)
+print('Is Queue Empty:',Q.isempty())
+Q.enqueue(7)
+print('Queue:')
+Q.display()
+print('Queue Length:', len(Q))
+Q.enqueue(12)
+print('Queue:')
+Q.display()
+print('Queue Length:', len(Q))
+ele = Q.dequeue()
+print('Queue:')
+Q.display()
+print('Queue Length:', len(Q))
+print('Removed Element:',ele)
+print('First Element:',Q.first())