Question

C PROGRAMMING

Create two void functions that 1) delete a specific value in a linked list and 2) delete all instances of that value. Both functions' only parameter is the number that will be erased.

Answer 1

Please find the code below.

CODE

/* Given a reference (pointer to pointer) to the head of a list

and a key, deletes the first occurrence of key in linked list */

void deleteNode(int key)

{

// Store head node

struct Node* temp = *head_ref, *prev;

// If head node itself holds the key to be deleted

if (temp != NULL && temp->data == key)

{

*head_ref = temp->next; // Changed head

free(temp); // free old head

return;

}

// Search for the key to be deleted, keep track of the

// previous node as we need to change 'prev->next'

while (temp != NULL && temp->data != key)

{

prev = temp;

temp = temp->next;

}

// If key was not present in linked list

if (temp == NULL) return;

// Unlink the node from linked list

prev->next = temp->next;

free(temp); // Free memory

}

/* Given a reference (pointer to pointer) to the head of a list and

a key, deletes all occurrence of the given key in linked list */

void deleteKey(int key)

{

// Store head node

struct Node* temp = *head_ref, *prev;

// If head node itself holds the key or multiple occurrences of key

while (temp != NULL && temp->data == key)

{

*head_ref = temp->next; // Changed head

free(temp); // free old head

temp = *head_ref; // Change Temp

}

// Delete occurrences other than head

while (temp != NULL)

{

// Search for the key to be deleted, keep track of the

// previous node as we need to change 'prev->next'

while (temp != NULL && temp->data != key)

{

prev = temp;

temp = temp->next;

}

// If key was not present in linked list

if (temp == NULL) return;

// Unlink the node from linked list

prev->next = temp->next;

free(temp); // Free memory

//Update Temp for next iteration of outer loop

temp = prev->next;

}

}

NOTE:

I have provided the code assuming that the linked list node is represented as:

// A linked list node

struct Node

{

    int data;

    struct Node *next;

};

struct Node* head; // points to the head of the linked list