Rearrange even & odd Nodes in a linked list

PROBLEM :

Given a singly linked list, rearrange it in a way that all odd position nodes are together and all even positions node are together,

Input: You have to complete the method which takes one argument: the head of the linked list. You should not read any input from stdin/console..
Note: There are multiple test cases, for each test case, this method will be called individually.

Output:
Your function should return pointer to head of the modified list.

Constraints:
1 <=T<= 50
1 <=N<= 100
1 <=value<= 1000

Example:
Input:
2
4
1 2 3 4
5
1 2 3 4 5

Output:
1 3 2 4
1 3 5 2 4
   
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SIMPLE c++ IMPLEMENTATION :
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/* Node structure
struct Node
{
    int data;
    struct Node* next;
}; */

// Should rearrange given linked list such that all even
// positioned Nodes are before odd positioned.
// Returns new head of linked List.

Node *rearrangeEvenOdd(Node *head)
{
    Node *even,*odd,*temp ;

    if(head==NULL)
        return head ;
     
    odd=head ;
    even=odd->next ;
    temp=even ;
 
    while(1)
    {
        if(even==NULL||odd==NULL||even->next==NULL)
        {
            odd->next=temp ;
            break ;
        }
        odd->next=even->next ;
        odd=odd->next ;
     
        if(odd->next==NULL)
        {
            even->next=NULL ;
            odd->next=temp ;
            break ;
        }
        even->next=odd->next ;
        even=even->next ;
    }
    return head ;
}

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SIMPLE c++ IMPLEMENTATION : (similar approch)
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/* Node structure
struct Node
{
    int data;
    struct Node* next;
}; */

// Should rearrange given linked list such that all even
// positioned Nodes are before odd positioned.
// Returns new head of linked List.
Node *rearrangeEvenOdd(Node *head)
{
    if(head==NULL||head->next==NULL)
        return head ;
       
    Node *first,*second ;
    first=head ;
    second=head->next ;
   
    Node *temp,*ptr ;
    ptr=first ;
    while(ptr->next->next!=NULL){
        temp=ptr->next ;
        ptr->next=ptr->next->next ;
        ptr=temp ;
    }
   
    temp=ptr->next ;
    temp->next=NULL ;
    ptr->next=NULL ;
   
    while(first->next!=NULL)
        first=first->next ;
       
    first->next=second ;
    return head ;
}

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