Design Circular Queue LeetCode solution in Java

1
class MyCircularQueue {
2

3
  private int front;
4
  private int rear;
5
  private int[] arr;
6
  private int cap;
7

8
  private int next(int i) { // to get next idx after i in circular queue
9
    return (i + 1) % cap;
10
  }
11

12
  private int prev(int i) { // to get prev idx before i in circular queue
13
    return (i + cap - 1) % cap;
14
  }
15

16
  // rest is as simple as implmenting a normal queue using array.
17
  public MyCircularQueue(int k) {
18
    arr = new int[k];
19
    cap = k;
20
    front = -1;
21
    rear = -1;
22
  }
23

24
  public boolean enQueue(int value) {
25
    if (isFull()) return false;
26
    if (front == -1) {
27
      front = 0;
28
      rear = 0;
29
      arr[rear] = value;
30
      return true;
31
    }
32
    rear = next(rear);
33
    arr[rear] = value;
34
    return true;
35
  }
36

37
  public boolean deQueue() {
38
    if (isEmpty()) return false;
39
    if (front == rear) {
40
      front = -1;
41
      rear = -1;
42
      return true;
43
    }
44
    front = next(front);
45
    return true;
46
  }
47

48
  public int Front() {
49
    if (front == -1) return -1;
50
    return arr[front];
51
  }
52

53
  public int Rear() {
54
    if (rear == -1) return -1;
55
    return arr[rear];
56
  }
57

58
  public boolean isEmpty() {
59
    return front == -1;
60
  }
61

62
  public boolean isFull() {
63
    return front != -1 && next(rear) == front;
64
  }
65
}