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  • 【leetcode】622. Design Circular Queue

    题目如下:

    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 cannot 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 [0, 1000].
    • The number of operations will be in the range of [1, 1000].
    • Please do not use the built-in Queue library.

    解题思路:用list就能搞定了。

    代码如下:

    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.capacity = k
            self.l = []
    
        def enQueue(self, value):
            """
            Insert an element into the circular queue. Return true if the operation is successful.
            :type value: int
            :rtype: bool
            """
            if len(self.l) >= self.capacity:
                return False
            self.l.append(value)
            return True
    
        def deQueue(self):
            """
            Delete an element from the circular queue. Return true if the operation is successful.
            :rtype: bool
            """
            if len(self.l) == 0:
                return False
            self.l.pop(0)
            return True
    
        def Front(self):
            """
            Get the front item from the queue.
            :rtype: int
            """
            return self.l[0] if len(self.l) > 0 else -1
    
        def Rear(self):
            """
            Get the last item from the queue.
            :rtype: int
            """
            return self.l[-1] if len(self.l) > 0 else -1
    
        def isEmpty(self):
            """
            Checks whether the circular queue is empty or not.
            :rtype: bool
            """
            return len(self.l) == 0
    
        def isFull(self):
            """
            Checks whether the circular queue is full or not.
            :rtype: bool
            """
            return len(self.l) == self.capacity
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  • 原文地址:https://www.cnblogs.com/seyjs/p/11398321.html
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