{"id":1011,"date":"2025-11-21T08:52:48","date_gmt":"2025-11-21T03:22:48","guid":{"rendered":"https:\/\/codexplained.in\/?p=1011"},"modified":"2025-11-21T08:52:48","modified_gmt":"2025-11-21T03:22:48","slug":"implementation-of-circular-queue-using-arrays","status":"publish","type":"post","link":"https:\/\/codexplained.in\/?p=1011","title":{"rendered":"Implementation of Circular Queue using Arrays"},"content":{"rendered":"\n

Steps for Implementation:<\/h3>\n\n\n\n
    \n
  1. Queue Representation<\/strong>:\n
      \n
    • We need an array to hold the queue elements.<\/li>\n\n\n\n
    • Two pointers, front<\/code> and rear<\/code>, will indicate the start and end of the queue.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
    • Enqueue Operation<\/strong>:\n
        \n
      • We add an element at the rear of the queue.<\/li>\n\n\n\n
      • If the queue is full, we can’t add any more elements.<\/li>\n\n\n\n
      • If the queue isn’t full, we move the rear pointer forward in a circular manner (using modulo %<\/code>).<\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • Dequeue Operation<\/strong>:\n
          \n
        • We remove an element from the front of the queue.<\/li>\n\n\n\n
        • If the queue is empty, we can’t remove any elements.<\/li>\n\n\n\n
        • After dequeuing, we move the front pointer forward in a circular manner.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
        • Check for Empty and Full Conditions<\/strong>:\n
            \n
          • A queue is empty<\/strong> if front == -1<\/code>.<\/li>\n\n\n\n
          • A queue is full<\/strong> if (rear + 1) % maxSize == front<\/code>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
          • Display Operation<\/strong>:\n
              \n
            • To display the queue, we need to traverse it starting from front<\/code> to rear<\/code> considering the circular nature.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n

              Program in C<\/h3>\n\n\n
              \n#include <stdio.h>\n#define MAX 5 \/\/ Define the maximum size of the circular queue\n\n\/\/ Circular Queue Structure\nstruct Circular Queue \n{\n    int items[MAX];\n    int front, rear;\n};\n\n\/\/ Function to initialize the queue\nvoid initialize Queue(struct Circular Queue *q) \n{\n    q->front = -1;\n    q->rear = -1;\n}\n\n\/\/ Function to check if the queue is full\nint is Full(struct Circular Queue *q) \n{\n    if ((q->rear + 1) % MAX == q->front) \n{\n        return 1;\n    }\n    return 0;\n}\n\n\/\/ Function to check if the queue is empty\nint is Empty(struct Circular Queue *q) \n{\n    if (q->front == -1) \n{\n        return 1;\n    }\n    return 0;\n}\n\n\/\/ Function to add an element to the circular queue\nvoid enqueue(struct Circular Queue *q, int value) \n{\n    if (is Full(q)) \n{\n        printf("Queue is Full!\\n");\n    } \nelse \n{\n        if (q->front == -1) \/\/ Inserting the first element\n            q->front = 0;\n        q->rear = (q->rear + 1) % MAX;\n        q->items[q->rear] = value;\n        printf("Inserted %d\\n", value);\n    }\n}\n\n\/\/ Function to remove an element from the circular queue\nint dequeue(struct Circular Queue *q) \n{\n    int element;\n    if (is Empty(q)) \n{\n        printf("Queue is Empty!\\n");\n        return -1;\n    } \nelse \n{\n        element = q->items[q->front];\n        if (q->front == q->rear) \n{ \/\/ Queue has only one element\n            q->front = -1;\n            q->rear = -1;\n        } \nelse \n{\n            q->front = (q->front + 1) % MAX;\n        }\n        printf("Deleted %d\\n", element);\n        return element;\n    }\n}\n\n\/\/ Function to display the circular queue\nvoid display(struct Circular Queue *q) \n{\n    int i;\n    if (is Empty(q)) \n{\n        printf("Queue is Empty!\\n");\n    } \nelse \n{\n        printf("Front -> %d\\n", q->front);\n        printf("Items -> ");\n        for (i = q->front; i != q->rear; i = (i + 1) % MAX) \n{\n            printf("%d ", q->items[i]);\n        }\n        printf("%d ", q->items[i]);\n        printf("\\nRear -> %d\\n", q->rear);\n    }\n}\n\n\/\/ Main function\nint main() \n{\n    struct Circular Queue q;\n    initialize Queue(&q);\n\n    \/\/ Test enqueue operation\n    enqueue(&q, 10);\n    enqueue(&q, 20);\n    enqueue(&q, 30);\n    enqueue(&q, 40);\n    enqueue(&q, 50); \/\/ Queue is full now\n\n    \/\/ Test display operation\n    display(&q);\n\n    \/\/ Test dequeue operation\n    dequeue(&q);\n    dequeue(&q);\n\n    \/\/ Display after two dequeue operations\n    display(&q);\n\n    \/\/ Enqueue after dequeue operations\n    enqueue(&q, 60);\n    display(&q);\n\n    return 0;\n}\n\n<\/pre><\/div>\n\n\n
              Explanation:<\/h3>\n\n\n\n
                \n
              1. initializeQueue()<\/strong>:\n
                  \n
                • Initializes the queue by setting both front<\/code> and rear<\/code> to -1<\/code>, which indicates an empty queue.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
                • isFull()<\/strong>:\n
                    \n
                  • Checks if the queue is full by checking if (rear + 1) % MAX == front<\/code>. This means that if the position just after rear<\/code> is front<\/code>, the queue is full.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
                  • isEmpty()<\/strong>:\n
                      \n
                    • Checks if the queue is empty by verifying if front == -1<\/code>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
                    • enqueue()<\/strong>:\n
                        \n
                      • Adds an element to the rear of the queue.<\/li>\n\n\n\n
                      • If the queue is empty, we set front<\/code> to 0<\/code> because we are inserting the first element.<\/li>\n\n\n\n
                      • Then, we update the rear<\/code> to the next position using (rear + 1) % MAX<\/code>.<\/li>\n\n\n\n
                      • Finally, the value is inserted at the rear<\/code> position.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
                      • dequeue()<\/strong>:\n
                          \n
                        • Removes the front element from the queue.<\/li>\n\n\n\n
                        • If the queue becomes empty after dequeuing (i.e., front == rear<\/code>), we reset both pointers to -1<\/code>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
                        • display()<\/strong>:\n
                            \n
                          • Prints the queue from the front to the rear, accounting for the circular nature by looping through indices using modulo.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n
                            Sample Output:<\/h3>\n\n\n
                            \nInserted 10\nInserted 20\nInserted 30\nInserted 40\nInserted 50\nQueue is Full!\nFront -> 0\nItems -> 10 20 30 40 50 \nRear -> 4\nDeleted 10\nDeleted 20\nFront -> 2\nItems -> 30 40 50 \nRear -> 4\nInserted 60\nFront -> 2\nItems -> 30 40 50 60 \nRear -> 0\n\n<\/pre><\/div>\n\n\n
                            Key Points:<\/h3>\n\n\n\n
                              \n
                            • Circular queues help in efficient use of space by reusing positions in the array once elements are dequeued.<\/li>\n\n\n\n
                            • The implementation uses simple operations like modulo arithmetic to wrap around the array when needed.<\/li>\n<\/ul>\n\n\n\n
                              <\/p>\n