Chapter 17, Problem 17RQE

A)

Explanation of Solution

Purpose of the given code:

The given code is trying to print the members of a linked list by traversing through the entire list by using a destructor. A destructor is called when the program ends or the destructor function calls.

Given Code:

//Definition of destructor

NumberList::printList()//Line 1

{//Line 2

//loop

//Error line3

while(head)//Line 3

{//Line 4

/*Print the data value of the node while traversing through the list*/

cout<<head->value; //Line5

/*the pointer is moved one position ahead till end of list */

head= head->next;//Line6

}//Line 7

}//Line 8

Error in the given code:

• In “line 3”, use of the head pointer to walk down the list destroys the list.
  • This should be written as an “auxiliary pointer”. So, correct code is given below:

    ListNode *nodePtr = head

          while (nodePtr != null)

                    ;&#x...

B)

Explanation of Solution

Purpose of the given code:

The given code is trying to print the members of a linked list by traversing through the entire list by using a destructor. A destructor is called when the program ends or the destructor function calls.

Given Code:

//Definition of destructor

NumberList::PrintList()//Line 1

{//Line 2

//Declaration of structure pointer variables

//Line3

ListNode *p =head; /*the start or head of the list is stored in p */

//loop

     //Error Line4

while (p->next) //Line4

{//Line 5

/*Print the data value of node p while traversing through the linklist */

//Line6

cout<<p->value; /*print the individual  data values of each node */

//Line7

p=p->next; //the pointer is moved one position ahead till end of list

}//Line8

}//Line9

Error in the given code:

• In “line 4”, eventually the pointer p becomes “NULL”, at which time the attempt to access p->NULL will result in an error.
  • This should be written by replacing the text p->next in the while loop with p.

while (p) //Line4

/*Here the loop will traverse till p exists or   till p is not NULL */

• The function fails to declare a return type of void...

C)

Explanation of Solution

Purpose of the given code:

The given code is trying to print the members of a linked list by traversing through the entire list by using a destructor. A destructor is called when the program ends or the destructor function calls.

Given Code:

//Definition of destructor

NumberList::PrintList()//Line 1

{//Line 2

//Declaration of structure pointer variables

//Line3

ListNode *p =head; /*the start or head of the list is stored in p */

//loop

     // Line4

while (p) //Line4

{//Line 5

/*Print the data value of node p while traversing through the linklist */

//Line6

cout<<p->value; /*print the individual  data values of each node */

          //Error Line7

//Line7

p++//the pointer is incremented by one position

}//Line8

}//Line9

Error in the given code:

• In “line 7”, the function uses p++ erroneously in place of p=p->next when attempting to move to the next node in the list. This is not possible as increment operator can work only on variables containing data values but here p is a node of a link list which contains an address value pointer pointing to the next list along with a data value.
  • This should be written by replacing the text p++ in the while loop body with p=p->next...

D)

Explanation of Solution

Purpose of the given code:

The given code is trying to destroy the members of a linked list by using a destructor. A destructor is called when the program ends or the destructor function calls.

Given Code:

//Definition of destructor

NumberList::~NumberList()//Line 1

{//Line 2

//Declaration of structure pointer variables

ListNode *nodePtr, *nextNode;//Line 3

//Storing "head" pointer into "nodePtr"

nodePtr = head;//Line 4

//loop

while (nodePtr != nullptr)//Line 5

{//Line 6

//Assign address of next into "nextNode"

nextNode = nodePtr->next;//Line 7

//Error

nodePtr->next=nullptr;//Line 8

//Assign nextNode into "nodePtr"

nodePtr = nextNode;//Line 9

}//Line 10

}//Line 11

Error in the given code:

In “line 8”, the address of “next” in “nodePtr” is assigned as “nullptr”.

• This should be written as “delete nodePtr” to delete the value of node from the list, because, “delete” operator is used to free the memory space allocated by the list...