641. Design Circular Deque.md

Problem

https://leetcode.com/problems/design-circular-deque/

Approach

• single array
• two pointers (front & end), wrap them around accordingly

Code

class MyCircularDeque {
    int *arr, front, end, k;
public:
    MyCircularDeque(int k) {
        arr = new int[k + 1];
        front = 0;
        end = k;
        this->k = k;
    }
    
    bool insertFront(int value) {
        if (isFull()) return false;
        arr[front] = value;
        ++front;
        if (front == k + 1) front = 0;
        return true;
    }
    
    bool insertLast(int value) {
        if (isFull()) return false;
        arr[end] = value;
        --end;
        if (end == -1) end = k;
        return true;
    }
    
    bool deleteFront() {
        if (isEmpty()) return false;
        --front;
        if (front == -1) front = k;
        return true;
    }
    
    bool deleteLast() {
        if (isEmpty()) return false;
        ++end;
        if (end == k + 1) end = 0;
        return true;
    }
    
    int getFront() {
        if (isEmpty()) return -1;
        return (front - 1 < 0)? arr[k] : arr[front - 1];
    }
    
    int getRear() {
        if (isEmpty()) return -1;
        return (end + 1 > k)? arr[0] : arr[end + 1];
    }
    
    bool isEmpty() {
        return (front - 1 < 0)? (end == k) : (front - 1 == end);
    }
    
    bool isFull() {
        return front == end;
    }
};