Some Important Linear Data Structures- at a glance
Queue is a specialized data storage structure (Abstract data type). Unlike, arrays access of elements in a Queue is restricted. It has two main operations enqueue and dequeue. Insertion in a queue is done using enqueue function and removal from a queue is done using dequeue function. An item can be inserted at the end (‘rear’) of the queue and removed from the front (‘front’) of the queue. It is therefore, also called First-In-First-Out (FIFO) list. Queue has five properties - capacity stands for the maximum number of elements Queue can hold, size stands for the current size of the Queue, elements is the array of elements, front is the index of first element (the index at which we remove the element) and rear is the index of last element (the index at which we insert the element).
Queue structure is defined with fields capacity, size, *elements (pointer to the array of elements), front and rear.
1. createQueue function– This function takes the maximum number of elements
(maxElements) the Queue can hold as an argument, creates a Queue according to it
and returns a pointer to the Queue.
2. enqueue function - This function takes the pointer to the top of the queue Q and the item
(element) to be inserted as arguments. Check for the emptiness of queue
3. dequeue function - This function takes the pointer to the top of the stack S as an
argument and will then dequeue an element.
4. front function – This function takes the pointer to the top of the queue Q as an argument and returns the front element of the queue Q.
1. Each function runs in O(1) time.
2. It has two basic implementations
Array-based implementation – It’s simple and efficient but the maximum size of
the queue is fixed.
Singly Linked List-based implementation – It’s complicated but there is no limit
on the queue size, it is subjected to the available memory.
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These are the standard sources of the knowledge expected from candidates interviewing at Google, Microsoft, Facebook, Amazon and other startups and top-tier technology companies. The books by Cormen or Sedgewick (a standard part of the undergraduate curriculum) are sufficient for this part of the preparation. Google specially, loves to focus on algorithmic questions.
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