CBSE Class 12 Computer Science Chapter 10: Queue NCERT Solutions

The `delque()` function removes the element from the front of the linked queue. It first checks if the queue is empty by verifying if the `front` pointer is `NULL`. If the queue is not empty, it stores the current `front` node in a temporary pointer `Temp`, displays the data of the node being deleted, and then updates the `front` pointer to the next node in the queue (`front = front->link`). If, after updating `front`, it becomes `NULL`, it means the queue is now empty, so the `rear` pointer is also set to `NULL`. Finally, the memory occupied by the deleted node is freed using `delete Temp;`.

void queue::delque() {

if (front != NULL) {

node *Temp = front;

cout << "Deleted Element: " << Temp->name << " " << Temp->marks << endl;

front = front->link;

delete Temp;

if(front == NULL)

rear = NULL;

} else {

cout << "Queue is empty" << endl; } }

(4 marks for correct program)

First, we define the structure for the queue node, which includes player number, player name, and a pointer to the next node. The function `QUEUEDEL` is designed to delete a player's information from the front of the linked queue. It takes the current `front` pointer as an argument. It checks if the queue is empty (`front == NULL`). If it is, an "Queue EMPTY" message is displayed. Otherwise, it uses a temporary pointer `temp` to hold the current `front` node. The data from this node (player number and name) is conceptually processed or displayed (though the provided snippet shows assignment to `val` and `val2` which are not used in the function signature, implying they might be for output or a different function design). The `front` pointer is then moved to the next node (`front = front->Link`), and the memory of the original front node is deallocated using `delete temp`. The function returns the updated `front` pointer.

Node Declaration:

struct node {

int PlayerNo;

char PlayerName[20];

Node*Link; }; Function to delete from Queue:

Node* QUEUEDEL(Node * front) { // Assuming val and val2 were placeholders or for a different purpose

Node *temp;

if (front == NULL) {

cout << "Queue EMPTY" << endl;

} else {

temp = front;

// Displaying or processing the deleted data (example):

cout << "Deleting Player No: " << temp->PlayerNo << ", Name: " << temp->PlayerName << endl;

front = front->Link;

delete temp; } return (front); } [1] indicates marks allocation in the original source.

The `QDELETE()` function is designed to remove a passenger's record from the front of a linked queue. It assumes the queue is managed by `front` and `rear` pointers, typically part of a `Queue` class. The function first checks if the queue is empty by testing if `front` is `NULL`. If the queue is empty, it prints a message indicating this. If the queue is not empty, it uses a temporary pointer `Temp` to point to the `front` node. The data from this node (passenger number and name) can be accessed via `Temp` for display or further processing before deletion. The `front` pointer is then advanced to the next node in the queue (`front = front->Link`). If advancing `front` makes it `NULL`, it signifies that the queue has become empty, and thus the `rear` pointer must also be set to `NULL`. Finally, the memory allocated for the node being removed is released using `delete Temp;`.

// Assuming this function is a member of a class with front and rear pointers

void QDELETE() {

if (front != NULL) {

node *Temp = front;

cout << "Deleting Passenger No: " << Temp->Pno << ", Name: " << Temp->Pname << endl;

front = front->Link;

delete Temp;

if (front == NULL) {

rear = NULL; // Update rear if the queue becomes empty } } else {

cout << "Queue is empty. Cannot delete."; } }