Chapter 17: Problem 11

Write a function double lastValue(ListNode *ptr) that returns the value stored in the last node of a nonempty list passed to it as parameter. The function should print an error message and terminate the program if the list passed to it is empty.

Short Answer

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Question: Write a function that takes a non-empty linked list as input and returns the value stored in the last node of the list. Answer: To write a function that returns the value stored in the last node of a non-empty linked list, follow these steps: 1. Declare the function with the name 'double lastValue(ListNode *ptr)', where 'ptr' is a pointer to the head of the linked list. 2. Check if the list is empty. If it is, print an error message and terminate the program. 3. Create a loop that iterates through the linked list until the last node is reached. 4. Return the value of the last node, which should be stored in the 'current' pointer after iteration.

Step by step solution

1. Function Declaration

Declare the function with the name 'double lastValue(ListNode *ptr)', where 'ptr' is a pointer to the head of the linked list.

2. Check if the list is empty

Inside the function, first check if the list passed to the function is empty. If it is, print an error message and terminate the program. To do this, you can use the 'if' statement: ```cpp if(ptr == nullptr){ cout << "Error: The list is empty." << endl; exit(EXIT_FAILURE); } ```

3. Iterate through the list

Now, create a loop that iterates through the linked list until the last node is reached. You can use a 'while' loop for this purpose: ```cpp ListNode *current = ptr; while(current->next != nullptr){ current = current->next; } ```

4. Return the value of the last node

At this point, the 'current' pointer should be pointing to the last node in the linked list. Simply return the value stored in this node: ```cpp return current->value; ``` Putting everything together, the final function will look like this: ```cpp double lastValue(ListNode *ptr){ if(ptr == nullptr){ cout << "Error: The list is empty." << endl; exit(EXIT_FAILURE); } ListNode *current = ptr; while(current->next != nullptr){ current = current->next; } return current->value; } ```

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Write a function double lastValue(ListNode *ptr) that returns the value stored in the last node of a nonempty list passed to it as parameter. The function should print an error message and terminate the program if the list passed to it is empty.

Short Answer

Step by step solution

1. Function Declaration

2. Check if the list is empty

3. Iterate through the list

4. Return the value of the last node

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