Question

hw3 Data Structure: Please write programs and finish the question in C language: thank you (You can do both 5 & 6 if you know both, or you can do any one of these 2 questions that you know, thank you!) 5. Generate a function for clockwise rotation each node (either char type or int type) in doubly linked list by N places, e.g. given list = NULL<-Head<=>c<=>i<=>v<=>i>=>c->NULL, from function call rotate DLL(list, 3), the output will be like this NULL<-Head<=>v<=>i<=>c<=>c>=>i->NULL 6. (Bonus) Check whether there exists random pointer in doubly linked list or not and correct it by a program, as example as follows for function input and output Input: => NULL NULLO Output: DHEAPPPPPDF NULL NULL

Answer 1

To rotate the Doubly linked list first check whether the given N is greater than the length of the list or not. If N is greater than the size of the list then deduce it in the range of linked list size by taking modulo with the length of the list. After that subtract the value of N from the length of the list. Now the problem reduces to the counter-clockwise rotation of a doubly-linked list by N places.

• Change the next of the last node to point the Head node.
• Change the prev of the Head node to point the last node.
• Change the value of the Head_ref to be the next of the Nth node.
• Change the value of next of the Nth Node to be NULL.
• Finally, make the prev of the Head node to point to NULL.

 #include <stdio.h> struct node{ int data; struct node *previous; struct node *next; }; struct node *head, *tail = NULL; int size = 0; void addNode(int data) { struct node *newNode = (struct node*)malloc(sizeof(struct node)); newNode->data = data; if(head == NULL) { head = tail = newNode; head->previous = NULL; tail->next = NULL; } else { tail->next = newNode; newNode->previous = tail; tail = newNode; tail->next = NULL; } size++; } void rotateList(int n) { //Initially, current will point to head struct node *current = head; //n should not be 0 or greater than or equal to number of nodes present in the list if(n == 0 || n >= size) return; else { //Traverse through the list till current point to nth node //after this loop, current will point to nth node for(int i = 1; i < n; i++) current = current->next; //Now to move entire list from head to nth node and add it after tail tail->next = head; //Node next to nth node will be new head head = current->next; //Previous node to head should be NULL head->previous = NULL; //nth node will become new tail of the list tail = current; //tail's next will point to NULL tail->next = NULL; } } void display() { struct node *current = head; if(head == NULL) { printf("List is empty\n"); return; } while(current != NULL) { printf("%d ", current->data); current = current->next; } printf("\n"); } int main() { addNode(1); addNode(2); addNode(3); addNode(4); addNode(5); printf("Original List: \n"); display(); rotateList(3); printf("Updated List: \n"); display(); return 0; } 

Original List: 1 2 3 4 5 Updated List: 4 5 1 2 3

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