Question

Write a c++ member function that sequentially searches for a specific element in a doubly linked list. return the position if found or -1 is the element cannot be found.

Answer 1

Write a c++ member function that sequentially searches for a specific element in a doubly linked list. return the position if found or -1 is the element cannot be found.

Code :-

​
#include <iostream>
using namespace std; 

struct Node 
{ 
        int data; 
        struct Node *next; 
        struct Node *prev; 
}; 

void insertNode(struct Node** start, int value) 
{ 
        if (*start == NULL) 
        { 
                struct Node* new_node = new Node; 
                new_node->data = value; 
                new_node->next = new_node->prev = new_node; 
                *start = new_node; 
                return; 
        } 

        Node *last = (*start)->prev; 
        struct Node* new_node = new Node; 
        new_node->data = value; 

        new_node->next = *start; 
 
        (*start)->prev = new_node; 
 
        new_node->prev = last; 

        last->next = new_node; 
} 

void displayList(struct Node* start) 
{ 
        struct Node *temp = start; 

        while (temp->next != start) 
        { 
                printf("%d ", temp->data); 
                temp = temp->next; 
        } 
        printf("%d ", temp->data); 
} 
 
int searchList(struct Node* start, int search) 
{ 
        struct Node *temp = start; 
        int count=0,flag=0,value; 

        if(temp == NULL) 
                return -1; 
        else
        { 
                while(temp->next != start) 
                { 
                        count++; 

                        if(temp->data == search) 
                        { 
                                flag = 1; 
                                count--; 
                                break; 
                        } 
                        temp = temp->next; 
                }
                if(temp->data == search) 
                { 
                        count++; 
                        flag = 1; 
                } 
                
                // If flag is true, then element found
                // else the element cannot be found so return -1
                if(flag == 1) 
                        cout<<"\n"<<search <<"\nfound at location "<<count<<endl; 
                else
                        cout<<"\n"<<search <<"\n-1"<<endl; 
        } 
} 

int main() 
{ 
        /* Start with the empty list */
        struct Node* start = NULL; 

        // Insert 17. So linked list becomes 17->NULL 
        insertNode(&start, 17); 

        // Insert 25. So linked list becomes 17->25 
        insertNode(&start, 25); 

        // Insert 9. So linked list 
        // becomes 17->25->9 
        insertNode(&start, 9); 

        // Insert 8. So linked list 
        // becomes 17->25->9->18 
        insertNode(&start, 18); 

        // Insert 6. So linked list 
        // becomes 17->25->9->18->6 
        insertNode(&start, 6); 

        printf("Created doubly linked list is: "); 
        displayList(start); 
        printf("\nEnter the element you want to search: ");
        searchList(start, 9); 
        
return 0;
}

​

Screenshot of code and output :-

Code :-

Output :-