Create design-circular-queue.py

Author: kamyu104

Python/design-circular-queue.py

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+# Time:  O(1)
+# Space: O(k)
+
+# Design your implementation of the circular queue.
+# The circular queue is a linear data structure in which
+# the operations are performed based on FIFO (First In First Out)
+# principle and the last position is connected back to
+# the first position to make a circle. It is also called ‘Ring Buffer’.
+# One of the Benefits of the circular queue is that
+# we can make use of the spaces in front of the queue.
+# In a normal queue, once the queue becomes full, 
+# we can not insert the next element even if there is a space in front of the queue.
+# But using the circular queue, we can use the space to store new values.
+# Your implementation should support following operations:
+#
+# MyCircularQueue(k): Constructor, set the size of the queue to be k.
+# Front: Get the front item from the queue. If the queue is empty, return -1.
+# Rear: Get the last item from the queue. If the queue is empty, return -1.
+# enQueue(value): Insert an element into the circular queue. Return true if the operation is successful.
+# deQueue(): Delete an element from the circular queue. Return true if the operation is successful.
+# isEmpty(): Checks whether the circular queue is empty or not.
+# isFull(): Checks whether the circular queue is full or not.
+# Example:
+#
+# MyCircularQueue circularQueue = new MycircularQueue(3); // set the size to be 3
+# circularQueue.enQueue(1);  // return true
+# circularQueue.enQueue(2);  // return true
+# circularQueue.enQueue(3);  // return true
+# circularQueue.enQueue(4);  // return false, the queue is full
+# circularQueue.Rear();  // return 3
+# circularQueue.isFull();  // return true
+# circularQueue.deQueue();  // return true
+# circularQueue.enQueue(4);  // return true
+# circularQueue.Rear();  // return 4
+#
+# Note:
+# - All values will be in the range of [1, 1000].
+# - The number of operations will be in the range of [1, 1000].
+# - Please do not use the built-in Queue library.
+
+class MyCircularQueue(object):
+
+    def __init__(self, k):
+        """
+        Initialize your data structure here. Set the size of the queue to be k.
+        :type k: int
+        """
+        self.__start = 0
+        self.__size = 0
+        self.__buffer = [0] * k
+
+    def enQueue(self, value):
+        """
+        Insert an element into the circular queue. Return true if the operation is successful.
+        :type value: int
+        :rtype: bool
+        """
+        if self.isFull():
+            return False
+        self.__buffer[(self.__start+self.__size) % len(self.__buffer)] = value
+        self.__size += 1
+        return True
+
+    def deQueue(self):
+        """
+        Delete an element from the circular queue. Return true if the operation is successful.
+        :rtype: bool
+        """
+        if self.isEmpty():
+            return False
+        self.__start = (self.__start+1) % len(self.__buffer)
+        self.__size -= 1
+        return True
+
+    def Front(self):
+        """
+        Get the front item from the queue.
+        :rtype: int
+        """
+        return -1 if self.isEmpty() else self.__buffer[self.__start]
+
+    def Rear(self):
+        """
+        Get the last item from the queue.
+        :rtype: int
+        """
+        return -1 if self.isEmpty() else self.__buffer[(self.__start+self.__size-1) % len(self.__buffer)]
+
+    def isEmpty(self):
+        """
+        Checks whether the circular queue is empty or not.
+        :rtype: bool
+        """
+        return self.__size == 0
+
+    def isFull(self):
+        """
+        Checks whether the circular queue is full or not.
+        :rtype: bool
+        """
+        return self.__size == len(self.__buffer)
+
+
+# Your MyCircularQueue object will be instantiated and called as such:
+# obj = MyCircularQueue(k)
+# param_1 = obj.enQueue(value)
+# param_2 = obj.deQueue()
+# param_3 = obj.Front()
+# param_4 = obj.Rear()
+# param_5 = obj.isEmpty()
+# param_6 = obj.isFull()