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data_structures/queue/DeQueue.py

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+from __future__ import print_function
+# 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 right 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)

data_structures/queue/QueueOnList.py

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+"""Queue represented by a python list"""
+class Queue():
+    def __init__(self):
+        self.entries = []
+        self.length = 0
+        self.front=0
+
+    def __str__(self):
+        printed = '<' + str(self.entries)[1:-1] + '>'
+        return printed
+
+    """Enqueues {@code item}
+    @param item
+        item to enqueue"""
+    def put(self, item):
+        self.entries.append(item)
+        self.length = self.length + 1
+
+
+    """Dequeues {@code item}
+    @requirement: |self.length| > 0
+    @return dequeued
+        item that was dequeued"""
+    def get(self):
+        self.length = self.length - 1
+        dequeued = self.entries[self.front]
+        self.front-=1
+        self.entries = self.entries[self.front:]
+        return dequeued
+
+    """Rotates the queue {@code rotation} times
+    @param rotation
+        number of times to rotate queue"""
+    def rotate(self, rotation):
+        for i in range(rotation):
+            self.put(self.get())
+
+    """Enqueues {@code item}
+    @return item at front of self.entries"""
+    def front(self):
+        return self.entries[0]
+
+    """Returns the length of this.entries"""
+    def size(self):
+        return self.length

data_structures/queue/QueueOnPseudoStack.py

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+"""Queue represented by a pseudo stack (represented by a list with pop and append)"""
+class Queue():
+    def __init__(self):
+        self.stack = []
+        self.length = 0
+
+    def __str__(self):
+        printed = '<' + str(self.stack)[1:-1] + '>'
+        return printed
+
+    """Enqueues {@code item}
+    @param item
+        item to enqueue"""
+    def put(self, item):
+        self.stack.append(item)
+        self.length = self.length + 1
+
+    """Dequeues {@code item}
+    @requirement: |self.length| > 0
+    @return dequeued
+        item that was dequeued"""
+    def get(self):
+        self.rotate(1)
+        dequeued = self.stack[self.length-1]
+        self.stack = self.stack[:-1]
+        self.rotate(self.length-1)
+        self.length = self.length -1
+        return dequeued
+
+    """Rotates the queue {@code rotation} times
+    @param rotation
+        number of times to rotate queue"""
+    def rotate(self, rotation):
+        for i in range(rotation):
+            temp = self.stack[0]
+            self.stack = self.stack[1:]
+            self.put(temp)
+            self.length = self.length - 1
+
+    """Reports item at the front of self
+    @return item at front of self.stack"""
+    def front(self):
+        front = self.get()
+        self.put(front)
+        self.rotate(self.length-1)
+        return front
+
+    """Returns the length of this.stack"""
+    def size(self):
+        return self.length