[Solved] Doubly Linked List Conversion Contest Problem

Doubly Linked List Conversion: Given a doubly linked with each of the previous pointer assigned to null. Your task is to assign previous pointer to each of previous nodes respectively.

Doubly Linked List Conversion Contest

Input Format :
First line of input contains number of testcases T.  For each testcase, first line of input contains length of linked list N and next line contains elements of linked list L[i].

Output Format :
For each testcase, print linked list in reverse order as per sample output shown below.

Task : Given all the other driver and utility  functions. Your task is to complete function to convert to doubly.

Constraints :
1<=T<=100
1<=N<=100
0<=L[i]<=10⁵

Example:
Input:
1
5
1 2 3 4 5
Output:
5 <- 4 <- 3 <- 2 <- 1 (single spaces on back and rear of each arrow)

Solution:

//Initial Template for C++

#include <bits/stdc++.h>
using namespace std;
struct Node
{
    int data;
    struct Node *next;
    struct Node *prev;
    
};


struct Node *newNode(int key){
    struct Node *temp=new Node;
    temp->data=key;
    temp->next=NULL;
    temp->prev=NULL;
    return temp;
}

struct Node *insertNode(struct Node *head,int key)
{
    if(head==NULL)
    head=newNode(key);
    else
    {
        head->next=insertNode(head->next,key);
    }
    return head;
}


void makeDoubly(struct Node *);


void traverse(struct Node *head)
{
    for(struct Node *temp=head;temp!=NULL;temp=temp->next)
    cout<<temp->data<<" ";
    cout<<endl;
}

void printBack(struct Node *head)
{
    if(head==NULL)
    return;
    struct Node *temp=head;
    while(temp->next)
    temp=temp->next;
    
    while(temp!=head)
    {
        cout<<temp->data<<" <- ";
        temp=temp->prev;
    }
    cout<<temp->data;
    cout<<endl;
}

int main() {
	int t;
	cin>>t;
	while(t--)
	{
	    struct Node *head=NULL;
	    int n;
	    cin>>n;
	    while(n--)
	    {
	        int x;
	        cin>>x;
	        head=insertNode(head,x);
	    }
	  //  traverse(head);
	    makeDoubly(head);
	    printBack(head);
	    
	}
	return 0;
}

//User function Template for C++


void makeDoubly(struct Node *head)
{
    //Your code here
    Node* a=head;
    Node* t=head;
	a=a->next;
	while(t->next!=NULL)
	{
		a->prev=t;
		a=a->next;
		t=t->next;
	}
}

Happy Learning – If you require any further information, feel free to contact me.