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In this post, we’ll talk about what a queue is and how it works. The queue is one of the most used data structures. The most helpful data structure in programming is a queue. The individual who joins the queue first receives the first ticket, similar to the queue for tickets outside a movie theatre. Let’s go further into queues and fundamental queue operations.
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The First In First Out (FIFO) rule is used in queues; the first item entered is the first item exited.<\/p>\n
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Since 1 was retained in the queue above before 2, it is also the first item to be taken out of the queue. The FIFO principle is followed.<\/p>\n
Enqueue and dequeue are programming phrases for adding and deleting items from a queue, respectively.<\/p>\n
Any programming language, including C, C++, Java, Python, or C#, can be used to implement the queue because the specification is basically the same.<\/p>\n
The following operations are possible with a queue, which is an object (abstract data structure – ADT):<\/p>\n
This function is used to see the data at the front of the queue. The peek() function’s algorithm is as follows \u2212<\/p>\n
Algorithm<\/strong><\/p>\n C programming language implementation of the peek() function \u2212<\/strong><\/p>\n We simply check for the rear pointer to reach at MAXSIZE to check that the queue is full because we are utilizing a single dimension array to create the queue. The algorithm will be different if we retain the queue as a circular linked list. The isfull() function’s algorithm \u2212<\/p>\n Algorithm<\/strong><\/p>\n C programming language implementation of the isfull() function \u2212<\/strong><\/p>\n This function is used to check if a queue is empty. We can say that a queue is empty if no element is present in it. Also we can find a queue is empty if the front is less than min or front is greater than rear.<\/p>\n Algorithm<\/strong><\/p>\n If the value of front is less than MIN or 0, it signifies that the queue is not yet initialized, hence empty.<\/p>\n C programming language implementation of the isempty() function \u2212<\/strong><\/p>\n Front and rear data pointers are kept in queues. As a result, compared to stack operations, its operations are more complex to implement.<\/p>\n To enqueue (insert) data into a queue, execute these instructions:<\/p>\n Step 1<\/strong>: Determine whether the queue is full.<\/p>\n Step 2<\/strong>: Produce an overflow error and quit if the queue is full.<\/p>\n Step 3<\/strong>: If the queue is not full, move the rear pointer forward to the next empty space.<\/p>\n Step 4<\/strong>: Where the rear is pointing, add the data element to the queue location.<\/p>\n Step 5<\/strong>: Return a success.<\/p>\n To prepare for any unforeseen circumstances, we may also check to verify if a queue has been initialized or not.<\/p>\n Algorithm for enqueue operation<\/strong><\/p>\n C programming language implementation of the enqueue() function \u2212<\/strong><\/p>\n It takes two steps to access data from a queue: first, access the data where the front is pointing, and second, remove the data after access. The dequeue operation is carried out in the manner described below:<\/p>\n Step1<\/strong>: Check whether the queue is empty.<\/p>\n Step 2<\/strong>: If there is no one in the queue, generate an underflow error and exit.<\/p>\n Step 3<\/strong>: Access the information at the front of the queue if it is not empty.<\/p>\n Step 4<\/strong>: Increment the front pointer to the next element.<\/p>\n Step 5<\/strong>: Successful return.<\/p>\n Algorithm for dequeue operation<\/strong><\/p>\n C programming language implementation of the dequeue() function \u2212<\/strong><\/p>\n Let’s combine and see the program having all the basic queue operations.<\/p>\n In Java and C++, queues are typically implemented using arrays. For Python, we make use of lists.<\/p>\n\t\t\t\t\t\tbegin procedure peek\n return queue[front]\nend procedure<\/code><\/pre>\nint peek() {\n return queue[front];\n}<\/code><\/pre>\nisfull()<\/h3>\n
begin procedure isfull\n\n if rear equals to MAXSIZE\n return true\n else\n return false\n endif\n\nend procedure<\/code><\/pre>\nbool isfull() {\n if(rear == MAXSIZE - 1)\n return true;\n else\n return false;\n}<\/code><\/pre>\nisempty()<\/h3>\n
begin procedure isempty\n\n if front is less than MIN OR front is greater than rear\n return true\n else\n return false\n endif\n\nend procedure<\/code><\/pre>\nbool isempty() {\n if(front < 0 || front > rear) \n return true;\n else\n return false;\n}<\/code><\/pre>\nEnqueue Operation<\/h3>\n
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<\/p>\nprocedure enqueue(data) \n\n if queue is full\n return overflow\n endif\n\n rear \u2190 rear + 1\n queue[rear] \u2190 data\n return true\n\nend procedure<\/code><\/pre>\nint enqueue(int data) \n if(isfull())\n return 0;\n\n rear = rear + 1;\n queue[rear] = data;\n\n return 1;<\/code><\/pre>\nDequeue Operation<\/h3>\n
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<\/p>\nprocedure dequeue\n\n if queue is empty\n return underflow\n end if\n\n data = queue[front]\n front \u2190 front + 1\n return true\n\nend procedure<\/code><\/pre>\nint dequeue() {\n if(isempty())\n return 0;\n\n int data = queue[front];\n front = front + 1;\n\n return data;\n}<\/code><\/pre>\nQueue Implementation in Python, Java, C, and C++<\/h2>\n