Chapter 20, Problem 2FTE

Program purpose:

The given program is used to implement queue using linked list.

Logical error:

Logical error is a mistake in a program’s source code that leads to produce an incorrect output. This error is a type of run time error, as it cannot be identified during the compilation of the program. This is a logical mistakes created by the programmer and it is determined when the program produces wrong output.

Error in the given code:

In the code, for inserting element to queue the statement “rear=new Node(x);” is used. Instead of it, user should use “rear.next=new Node(x)”. Because, when using the statement “rear=new Node(x)” every time, the value of the “rear” is changing instead of adding new element. In the corrected statement, the “rear.next” is set as pointing to a new element (x).

Correct statement:

//creating node containing x, set rear.next to point that node.

rear.next=new Node(x);

Corrected code:

//method enqueue is for adding a new value to the queue.

void enqueue(int x)

{

    //if the queue is empty

    if (empty())

    {

//set rear to pointing to a new node with value x...