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@ -34,50 +34,9 @@
* to build a ring with a fixed size array, any of the elements could be considered as the head.
* to enqueue, you loop the queue with the tail index until you find a `None` (even if it has to loop back):
<br>
```python
while self.queue[self.tail] is not None:
self.tail += 1
if self.tail == self.size:
self.tail = 0
self.queue[self.tail] = value
```
<br>
* to dequeue, you simply pop the head value:
<br>
```python
value = self.queue[self.head]
self.queue[self.head] = None
self.head += 1
```
<br>
* as long as we know the length of the queue, we can instantly locate its tails based on this formula:
<br>
```
tail_index = (head_index + current_length - 1) % size
```
<br>
* there is one occasion when `tail` index is set to zero:
* when the enqueue operation adds to the last position in the array and tail has to loop back (`self.tail == self.size`).
* there are two occasions when `head` index is set to zero:
* when the queue is checked as empty
* when the dequeue operation popped the last element in the array and head has to loop back (`self.head == self.size`).
<br>
```python
class CircularQueue:
@ -135,6 +94,54 @@ class CircularQueue:
return True
```
<br>
* to enqueue, you loop the queue with the tail index until you find a `None` (even if it has to loop back):
<br>
```python
while queue[self.tail]:
self.tail += 1
if self.tail == self.size:
self.tail = 0
self.queue[self.tail] = value
```
<br>
* to dequeue, you simply pop the head value:
<br>
```python
value = self.queue[self.head]
self.queue[self.head] = None
self.head += 1
```
<br>
* as long as we know the length of the queue, we can instantly locate its tails based on this formula:
<br>
```
tail_index = (head_index + current_length - 1) % size
```
<br>
* there is one occasion when `tail` index is set to zero:
* when the enqueue operation adds to the last position in the array and tail has to loop back (`self.tail == self.size`).
* there are two occasions when `head` index is set to zero:
* when the queue is checked as empty
* when the dequeue operation popped the last element in the array and head has to loop back (`self.head == self.size`).
<br>
* another version used only one index (for `head`) and calculate the tail with the equation:
@ -167,7 +174,7 @@ class CircularQueue:
<br>
* * in this example we also implement the methods `is_empty` and `is_full` using an extra counter variable `self.count` that can be compared to `self.size` or `0` and used to validate `rear` and `front`.
* * in the example below we also implement the methods `is_empty` and `is_full` using an extra counter variable `self.count` that can be compared to `self.size` or `0` and used to validate `rear` and `front`.
<br>