A Queue<\/strong> is a data structure that works on the FIFO<\/strong> principle, which stands for First In, First Out<\/strong>. This means that the first element added to the queue will be the first one to be removed, just like waiting in a line\u2014those who arrive first get served first.<\/p>\n\n\n\n Now, let’s get into the code implementation using arrays.<\/p>\n\n\n\n Here\u2019s the C program to implement a Queue using arrays:<\/p>\n\n\n This code demonstrates a simple queue using arrays and includes boundary checks for overflow (when the queue is full) and underflow (when the queue is empty).<\/p>\n\n\n\n <\/p>\n\n
Steps for Queue Implementation<\/h3>\n\n\n\n
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front<\/code> will point to the first element.<\/li>\n\n\n\nrear<\/code> will point to the last element.<\/li>\n<\/ul>\n<\/li>\n\n\n\n\n
\n#include <stdio.h>\n#include <stdlib.h>\n\n#define MAX 5 \/\/ Define the maximum size of the queue\n\n\/\/ Declare the Queue structure\nstruct Queue {\n int items[MAX];\n int front;\n int rear;\n};\n\n\/\/ Function to create an empty queue\nvoid createQueue(struct Queue* q) \n{\n q->front = -1;\n q->rear = -1;\n}\n\n\/\/ Check if the queue is full\nint isFull(struct Queue* q) \n{\n if (q->rear == MAX - 1) \n return 1;\n else\n return 0;\n}\n\n\/\/ Check if the queue is empty\nint isEmpty(struct Queue* q) \n{\n if (q->front == -1 || q->front > q->rear) \n return 1;\n else\n return 0;\n}\n\n\/\/ Function to add an element to the queue\nvoid enqueue(struct Queue* q, int value) \n{\n if (isFull(q)) \n{\n printf("Queue is Full! Cannot insert %d\\n", value);\n } else {\n if (q->front == -1) \n{\n q->front = 0; \/\/ Set front to 0 if the queue was empty\n }\n q->rear++;\n q->items[q->rear] = value;\n printf("Inserted %d into the queue\\n", value);\n }\n}\n\n\/\/ Function to remove an element from the queue\nint dequeue(struct Queue* q) \n{\n int item;\n if (isEmpty(q)) \n{\n printf("Queue is Empty! Nothing to dequeue\\n");\n return -1;\n } \nelse \n{\n item = q->items[q->front];\n q->front++;\n if (q->front > q->rear)\n{\n q->front = q->rear = -1; \/\/ Reset the queue when all elements are dequeued\n }\n printf("Removed %d from the queue\\n", item);\n return item;\n }\n}\n\n\/\/ Function to display the queue\nvoid display(struct Queue* q) \n{\n if (isEmpty(q)) \n{\n printf("Queue is empty\\n");\n } else \n{\n printf("Queue elements are: ");\n for (int i = q->front; i <= q->rear; i++) \n{\n printf("%d ", q->items[i]);\n }\n printf("\\n");\n }\n}\n\n\/\/ Main function to demonstrate the operations of the queue\nint main() \n{\n struct Queue q;\n createQueue(&q);\n \n \/\/ Enqueue elements\n enqueue(&q, 10);\n enqueue(&q, 20);\n enqueue(&q, 30);\n enqueue(&q, 40);\n enqueue(&q, 50);\n \n \/\/ Display queue\n display(&q);\n \n \/\/ Try to enqueue when queue is full\n enqueue(&q, 60);\n \n \/\/ Dequeue elements\n dequeue(&q);\n dequeue(&q);\n \n \/\/ Display queue after dequeue\n display(&q);\n \n return 0;\n}\n\n<\/pre><\/div>\n\n\nExplanation:<\/h3>\n\n\n\n
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Queue<\/code> structure consists of:\n\n
items[]<\/code>: An array to store the elements of the queue.<\/li>\n\n\n\nfront<\/code>: Points to the first element in the queue.<\/li>\n\n\n\nrear<\/code>: Points to the last element in the queue.<\/li>\n<\/ul>\n<\/li>\n\n\n\nfront<\/code> and rear<\/code> set to -1, indicating an empty queue.<\/li>\n\n\n\nrear<\/code> pointer has reached the maximum size (MAX - 1<\/code>), meaning no more elements can be inserted.<\/li>\n\n\n\nfront<\/code> is -1 or greater than rear<\/code>.<\/li>\n\n\n\n\n
rear<\/code> and add the element to the items[]<\/code> array.<\/li>\n\n\n\nfront<\/code> to 0.<\/li>\n<\/ul>\n<\/li>\n\n\n\n\n
items[front]<\/code> and increment front<\/code>.<\/li>\n\n\n\nfront<\/code> and rear<\/code> to -1.<\/li>\n<\/ul>\n<\/li>\n\n\n\nfront<\/code> to rear<\/code>.<\/li>\n<\/ol>\n\n\n\nOutput:<\/h3>\n\n\n
\nInserted 10 into the queue\nInserted 20 into the queue\nInserted 30 into the queue\nInserted 40 into the queue\nInserted 50 into the queue\nQueue elements are: 10 20 30 40 50 \nQueue is Full! Cannot insert 60\nRemoved 10 from the queue\nRemoved 20 from the queue\nQueue elements are: 30 40 50 \n<\/pre><\/div>\n\n\n