leetcode641.设计循环双端队列

题目链接

题解:

类似的题目为：leetcode622题设计循环队列，622题的 题解 先附上。
本题和622题是一样的，注意的点也在我的题解上有详细的说明，在这里就不重复了。底层依旧是使用数组，以及两个指针front,tail分别标记队首元素和下一个addLast的添加位置。代码如下：

class MyCircularDeque {

    private int[] data;
    private int front;
    private int tail;

    /** Initialize your data structure here. Set the size of the deque to be k. */
    public MyCircularDeque(int k) {
        data = new int[k + 1];
        front = 0;
        tail = 0;
    }
    
    private int getSize(){
        if(tail < front){
            return data.length - front + tail;
        }else{
            return tail - front;
        }
    }

    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    public boolean insertFront(int value) {
        if(isFull()){
            return false;
        }else{
            front = (front + data.length - 1) % data.length;
            data[front] = value;
            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;
        }else{
            data[tail] = value;
            tail = (tail + 1) % data.length;
            return true;
        }
    }
    
    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    public boolean deleteFront() {
        if(getSize() == 0){
            return false;
        }else{
            front = (front + 1) % data.length;
            return true;
        }
    }
    
    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    public boolean deleteLast() {
        if(getSize() == 0){
            return false;
        }else{
            tail = (tail + data.length - 1) % data.length;
            return true;
        }
    }
    
    /** Get the front item from the deque. */
    public int getFront() {
        if(front == tail){
            return -1;
        }else{
            return data[front];
        }
    }
    
    /** Get the last item from the deque. */
    public int getRear() {
        if(front == tail){
            return -1;
        }else{
            return data[(front + getSize() - 1) % data.length];
        }
    }
    
    /** Checks whether the circular deque is empty or not. */
    public boolean isEmpty() {
        return front == tail;
    }
    
    /** Checks whether the circular deque is full or not. */
    public boolean isFull() {
        return getSize() == data.length - 1;
    }
}

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * MyCircularDeque obj = new MyCircularDeque(k);
 * boolean param_1 = obj.insertFront(value);
 * boolean param_2 = obj.insertLast(value);
 * boolean param_3 = obj.deleteFront();
 * boolean param_4 = obj.deleteLast();
 * int param_5 = obj.getFront();
 * int param_6 = obj.getRear();
 * boolean param_7 = obj.isEmpty();
 * boolean param_8 = obj.isFull();
 */

执行结果如下：