Question

1. Build a double linked list with 5 in the first node following the instructions: Insert a node with 3 at the top of the list Insert a node with 10 at the bottom of the list Insert a node with 7 between nodes with 5 and 10 2. Start deleting nodes from the list in the following order; Delete the node with 7 Delete the node with 3 Delete the node with 10 3. Print the resulting list forward and backwards. write your statements in C.

Answer 1

code: doublyLinkedList.c

#include<stdio.h>
#include<stdlib.h>

typedef struct node{
        int data;
        struct node *next, *prev;
}Node;

void displayList(Node *head){
        Node *p = head, *r, *q;
        r = q = p;
        printf("Forward->\n");
        while(p){
                printf("%d, ",p->data);
                r=p;
                p = p->next;
        }
        printf("\n<-Backward\n");
        while(r){
                printf("%d, ", r->data);
                r= r->prev;
        }
        printf("\n");
}

Node * createNode(int data){
        Node * p = (Node *)malloc(sizeof(Node));
        p->data = data;
        p->next = NULL;
        p->prev = NULL; 
        return p;
}

Node * addNodeToList(Node *head, int data){
        Node *p, *q, *r;
        q = createNode(data);
        if(head==NULL){
                head = q;
                return head;
        }
        if(head->next==NULL){
                if(head->data > data){
                        q->next = head;
                        q->next->prev = q;
                        head = q;
                }
                else{
                        head->next = q;
                        q->prev = head;
                }
                return head;
        }
        p = head;
        while(p && p->data < data){
                r = p;
                p = p->next;
        }
        if(p==NULL){
                r->next = q;
                q->prev = r;
        }
        else{
                r->next = q;
                q->next = p;
                q->prev = r;
                p->prev = q;
        }
        return head;
}

Node * deleteNodeFromList(Node *head, int key){
        Node *p, *r;
        if(head==NULL){
                return head;
        }
        if(head->next==NULL && head->data==key){
                p = head;
                free(p);
                head = NULL;
                return head;
        }
        if(head->data==key && head->next!=NULL){
                p = head;
                head = p->next;
                head->prev = NULL;
                free(p);
                return head;
        }
        p = head;
        while(p && p->data != key){
                r = p;
                p = p->next;
        }
        if(p==NULL){
                return ;
        }
        else{
                if(p->next==NULL){
                        r->next = NULL;
                }
                else{
                        p->next->prev = r;
                        r->next = p->next;        
                }
                free(p);
        }
        return head;
}


int main(void){
        Node *list = NULL;
        list = addNodeToList(list, 5);  
        list = addNodeToList(list, 3);
        list = addNodeToList(list, 10);
        list = addNodeToList(list, 7);
        list = deleteNodeFromList(list, 7);
        list = deleteNodeFromList(list, 3);
        list = deleteNodeFromList(list, 10);
        displayList(list);
        return 0;
}

output: