Flattening a Linked List

//{ Driver Code Starts
#include <bits/stdc++.h>

struct Node{
    int data;
    struct Node * next;
    struct Node * bottom;

    Node(int x){
        data = x;
        next = NULL;
        bottom = NULL;
    }

};

using namespace std;

void printList(Node *Node)
{
    while (Node != NULL)
    {
        printf("%d ", Node->data);
        Node = Node->bottom;
    }
}

Node* flatten (Node* root);

int main(void) {

    int t;
    cin>>t;
    while(t--){
    int n,m,flag=1,flag1=1;
    struct Node * temp=NULL;
    struct Node * head=NULL;
    struct Node * pre=NULL;
    struct Node * tempB=NULL;
    struct Node * preB=NULL;
        cin>>n;
        int work[n];
        for(int i=0;i<n;i++)
            cin>>work[i];
        for(int i=0;i<n;i++){
            m=work[i];
            --m;
            int data;
            scanf("%d",&data);
            temp = new Node(data);
            temp->next = NULL;
            temp->bottom = NULL;

            if(flag){
                head = temp;
                pre = temp;
                flag = 0;
                flag1 = 1;
            }
            else{
                pre->next = temp;
                pre = temp;
                flag1 = 1;
            }
            for(int j=0;j<m;j++){

                int temp_data;
                scanf("%d",&temp_data);
                tempB = new Node(temp_data);

                if(flag1){
                    temp->bottom=tempB;
                    preB=tempB;
                    flag1=0;
                }
                else{
                    preB->bottom=tempB;
                    preB=tempB;
                }
            }
        }
           Node *fun = head;
           Node *fun2=head;

            Node* root = flatten(head);
            printList(root);
            cout<<endl;

    }
    return 0;
}

// } Driver Code Ends


/* Node structure  used in the program

struct Node{
    int data;
    struct Node * next;
    struct Node * bottom;

    Node(int x){
        data = x;
        next = NULL;
        bottom = NULL;
    }

};
*/

/*  Function which returns the  root of
    the flattened linked list. */

Node* Merge(Node* a,Node* b)
{
    if(a==NULL)
    {
        return b;
    }
    if(b==NULL)
    {
        return a;
    }
    Node* result;
    if(a->data < b->data)
    {
        result=a;
        result->bottom = Merge(a->bottom,b);
    }
    else
    {
        result=b;
        result->bottom = Merge(a,b->bottom);
    }
    result->next=NULL;
    return result;
}

Node *flatten(Node *root)
{
   // Your code here
   if(root==NULL || root->next==NULL)
   {
       return root;
   }
   root->next=flatten(root->next);

   root=Merge(root,root->next);
   return root;
}
// https://practice.geeksforgeeks.org/problems/flattening-a-linked-list/