641. 设计循环双端队列-优快云博客

本文链接：https://blog.youkuaiyun.com/weixin_39590058/article/details/108866906

这个博客介绍了一个名为MyCircularDeque的数据结构实现，它是一个环形双端队列。该数据结构支持在队列前端插入和删除元素，以及在队列后端插入和删除元素，并提供了获取队列前端和后端元素的方法。博客详细说明了每个操作的逻辑，包括判断队列是否已满或为空的辅助方法。

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class MyCircularDeque {
    int size = 0;
    int[] nums;
    int start = 0;
    int end = -1;

    /** Initialize your data structure here. Set the size of the deque to be k. */
    public MyCircularDeque(int k) {
        nums = new int[k];
    }

    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    public boolean insertFront(int value) {
        if (isFull()) return false;

        if (isEmpty()) {
            start = 0;
            end = 0;
        } else {
            start = (start == 0 ? nums.length - 1 : start - 1);
        }
        
        nums[start] = value;
        size++;
        return true;
    }

    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    public boolean insertLast(int value) {
        if (isFull()) return false;

        end = (end + 1) % nums.length;
        nums[end] = value;
        size++;
        return true;
    }

    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    public boolean deleteFront() {
        if (isEmpty()) return false;

        start = (start + 1) % nums.length;
        size--;
        return true;
    }

    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    public boolean deleteLast() {
        if (isEmpty()) return false;

        end = (end == 0 ? nums.length-1 : end-1);
        size--;
        return true;
    }

    /** Get the front item from the deque. */
    public int getFront() {
        return isEmpty() ? -1 : nums[start];
    }

    /** Get the last item from the deque. */
    public int getRear() {
        return isEmpty() ? -1 : nums[end];
    }

    /** Checks whether the circular deque is empty or not. */
    public boolean isEmpty() {
        return size == 0;
    }

    /** Checks whether the circular deque is full or not. */
    public boolean isFull() {
        return size == nums.length;
    }
}