双端队列-双链表和固定数组实现

// 设计循环双端队列
// 测试链接 : https://leetcode.cn/problems/design-circular-deque/
public class CircularDeque {

	// 提交时把类名、构造方法改成 : MyCircularDeque
	// 其实内部就是双向链表
	// 常数操作慢，但是leetcode数据量太小了，所以看不出劣势
	class MyCircularDeque1 {

		public Deque<Integer> deque = new LinkedList<>();
		public int size;
		public int limit;

		public MyCircularDeque1(int k) {
			size = 0;
			limit = k;
		}

		public boolean insertFront(int value) {
			if (isFull()) {
				return false;
			} else {
				deque.offerFirst(value);
				size++;
				return true;
			}
		}

		public boolean insertLast(int value) {
			if (isFull()) {
				return false;
			} else {
				deque.offerLast(value);
				size++;
				return true;
			}
		}

		public boolean deleteFront() {
			if (isEmpty()) {
				return false;
			} else {
				size--;
				deque.pollFirst();
				return true;
			}
		}

		public boolean deleteLast() {
			if (isEmpty()) {
				return false;
			} else {
				size--;
				deque.pollLast();
				return true;
			}
		}

		public int getFront() {
			if (isEmpty()) {
				return -1;
			} else {
				return deque.peekFirst();
			}
		}

		public int getRear() {
			if (isEmpty()) {
				return -1;
			} else {
				return deque.peekLast();
			}
		}

		public boolean isEmpty() {
			return size == 0;
		}

		public boolean isFull() {
			return size == limit;
		}

	}

	// 提交时把类名、构造方法改成 : MyCircularDeque
	// 自己用数组实现，常数操作快，但是leetcode数据量太小了，看不出优势
	class MyCircularDeque2 {

		public int[] deque;
		public int l, r, size, limit;

		public MyCircularDeque2(int k) {
			deque = new int[k];
			l = r = size = 0;
			limit = k;
		}

		public boolean insertFront(int value) {
			if (isFull()) {
				return false;
			} else {
				if (isEmpty()) {
					l = r = 0;
					deque[0] = value;
				} else {
					l = l == 0 ? (limit - 1) : (l - 1);
					deque[l] = value;
				}
				size++;
				return true;
			}
		}

		public boolean insertLast(int value) {
			if (isFull()) {
				return false;
			} else {
				if (isEmpty()) {
					l = r = 0;
					deque[0] = value;
				} else {
					r = r == limit - 1 ? 0 : (r + 1);
					deque[r] = value;
				}
				size++;
				return true;
			}
		}

		public boolean deleteFront() {
			if (isEmpty()) {
				return false;
			} else {
				l = (l == limit - 1) ? 0 : (l + 1);
				size--;
				return true;
			}
		}

		public boolean deleteLast() {
			if (isEmpty()) {
				return false;
			} else {
				r = r == 0 ? (limit - 1) : (r - 1);
				size--;
				return true;
			}
		}

		public int getFront() {
			if (isEmpty()) {
				return -1;
			} else {
				return deque[l];
			}
		}

		public int getRear() {
			if (isEmpty()) {
				return -1;
			} else {
				return deque[r];
			}
		}

		public boolean isEmpty() {
			return size == 0;
		}

		public boolean isFull() {
			return size == limit;
		}

	}

}

双端队列-双链表和固定数组实现