859. Design Circular Deque¶

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859. Design Circular Deque

Medium

Design your implementation of the circular double-ended queue (deque).

Implement the MyCircularDeque class:

• MyCircularDeque(int k) Initializes the deque with a maximum size of k.
• boolean insertFront() Adds an item at the front of Deque. Returns true if the operation is successful, or false otherwise.
• boolean insertLast() Adds an item at the rear of Deque. Returns true if the operation is successful, or false otherwise.
• boolean deleteFront() Deletes an item from the front of Deque. Returns true if the operation is successful, or false otherwise.
• boolean deleteLast() Deletes an item from the rear of Deque. Returns true if the operation is successful, or false otherwise.
• int getFront() Returns the front item from the Deque. Returns -1 if the deque is empty.
• int getRear() Returns the last item from Deque. Returns -1 if the deque is empty.
• boolean isEmpty() Returns true if the deque is empty, or false otherwise.
• boolean isFull() Returns true if the deque is full, or false otherwise.

Example 1:

Input
["MyCircularDeque", "insertLast", "insertLast", "insertFront", "insertFront", "getRear", "isFull", "deleteLast", "insertFront", "getFront"]
[[3], [1], [2], [3], [4], [], [], [], [4], []]
Output
[null, true, true, true, false, 2, true, true, true, 4]

Explanation
MyCircularDeque myCircularDeque = new MyCircularDeque(3);
myCircularDeque.insertLast(1);  // return True
myCircularDeque.insertLast(2);  // return True
myCircularDeque.insertFront(3); // return True
myCircularDeque.insertFront(4); // return False, the queue is full.
myCircularDeque.getRear();      // return 2
myCircularDeque.isFull();       // return True
myCircularDeque.deleteLast();   // return True
myCircularDeque.insertFront(4); // return True
myCircularDeque.getFront();     // return 4

Constraints:

• 1 <= k <= 1000
• 0 <= value <= 1000
• At most 2000 calls will be made to insertFront, insertLast, deleteFront, deleteLast, getFront, getRear, isEmpty, isFull.

Solution¶

class MyCircularDeque {
    private Deque<Integer> dq;
    private int len;
    public MyCircularDeque(int k) {
        dq = new ArrayDeque<>();
        this.len = k;
    }
    public boolean insertFront(int value) {
        if (dq.size() == len) return false;
        dq.addFirst(value);
        return true;
    }
    public boolean insertLast(int value) {
        if (dq.size() == len) return false;
        dq.addLast(value);
        return true;
    }
    public boolean deleteFront() {
        if (dq.size() == 0) return false;
        dq.pollFirst();
        return true;
    }
    public boolean deleteLast() {
        if (dq.size() == 0) return false;
        dq.pollLast();
        return true;
    }
    public int getFront() {
        if (dq.size() == 0) return -1;
        return dq.peekFirst();
    }
    public int getRear() {
        if (dq.size() == 0) return -1;
        return dq.peekLast();
    }
    public boolean isEmpty() {
        return dq.size() == 0;
    }
    public boolean isFull() {
        return dq.size() == len;
    }
}
/**
 * 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();
 */

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here