A queue is a data structure that follows the First In First Out(FIFO) principle.
This means that the first item added to the queue will be the first one to be removed. A queue can be implemented using an array.
To add an item to the queue, we use push method of the array. This method adds an element to the end of the array.
To remove an itme from the queue, we use the shift() method of the array. This method removes the first element of the array and returns it.
Adding and removing items is O(1) operation
- Arrays have index associated with them
- Shifting indexes is O(n) operation linearly (quite expensive)
| Lookup | enqueue | dequeue | peek |
|---|---|---|---|
| O(n) | O(1) | O(1) | O(1) |
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enqueue(element) : adds an element to the end of the queue by using the push() method of the array. This method takes one parameter, the element to be added to the queue.
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dequeue() : removes the first element of the queue and returns it by using the shift() method of the array. If the queue is empty, it returns "Underflow"
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front() : returns the first element of the queue without removing it. If the queue is empty, it returns "No elements in Queue"
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isEmpty() : returns a boolean value indicating whether the queue is empty or not. It returns true if the queue is empty, false otherwise.
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printQueue() : returns the string representation of the queue elements. It loops through the queue elements and concatenates it to the string variable and returns it.