Problem
Design your implementation of the circular double-ended queue (deque).
Your implementation should support following operations:
- MyCircularDeque(k): Constructor, set the size of the deque to be k.
- insertFront(): Adds an item at the front of Deque. Return true if the operation is successful.
- insertLast(): Adds an item at the rear of Deque. Return true if the operation is successful.
- deleteFront(): Deletes an item from the front of Deque. Return true if the operation is successful.
- deleteLast(): Deletes an item from the rear of Deque. Return true if the operation is successful.
- getFront(): Gets the front item from the Deque. If the deque is empty, return -1.
- getRear(): Gets the last item from Deque. If the deque is empty, return -1.
- isEmpty(): Checks whether Deque is empty or not.
- isFull(): Checks whether Deque is full or not.
Example:
MyCircularDeque circularDeque = new MycircularDeque(3); // set the size to be 3 circularDeque.insertLast(1); // return true circularDeque.insertLast(2); // return true circularDeque.insertFront(3); // return true circularDeque.insertFront(4); // return false, the queue is full circularDeque.getRear(); // return 32 circularDeque.isFull(); // return true circularDeque.deleteLast(); // return true circularDeque.insertFront(4); // return true circularDeque.getFront(); // return 4
Note:
- All values will be in the range of [1, 1000].
- The number of operations will be in the range of [1, 1000].
- Please do not use the built-in Deque library.
Solution
Using head and tail to pointer to the head and the tail in the circular buffer.
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// Author: Huahua // Running time: 20 ms class MyCircularDeque { public: /** Initialize your data structure here. Set the size of the deque to be k. */ MyCircularDeque(int k): k_(k), q_(k), head_(1), tail_(-1), size_(0) {} /** Adds an item at the front of Deque. Return true if the operation is successful. */ bool insertFront(int value) { if (isFull()) return false; head_ = (head_ - 1 + k_) % k_; q_[head_] = value; if (size_ == 0) tail_ = head_; ++size_; return true; } /** Adds an item at the rear of Deque. Return true if the operation is successful. */ bool insertLast(int value) { if (isFull()) return false; tail_ = (tail_ + 1 + k_) % k_; q_[tail_] = value; if (size_ == 0) head_ = tail_; ++size_; return true; } /** Deletes an item from the front of Deque. Return true if the operation is successful. */ bool deleteFront() { if (isEmpty()) return false; head_ = (head_ + 1 + k_) % k_; --size_; return true; } /** Deletes an item from the rear of Deque. Return true if the operation is successful. */ bool deleteLast() { if (isEmpty()) return false; tail_ = (tail_ - 1 + k_) % k_; --size_; return true; } /** Get the front item from the deque. */ int getFront() { if (isEmpty()) return -1; return q_[head_]; } /** Get the last item from the deque. */ int getRear() { if (isEmpty()) return -1; return q_[tail_]; } /** Checks whether the circular deque is empty or not. */ bool isEmpty() { return size_ == 0; } /** Checks whether the circular deque is full or not. */ bool isFull() { return size_ == k_; } private: const int k_; int head_; int tail_; int size_; vector<int> q_; }; |