GATE | Sudo GATE 2020 Mock I (27 December 2019) | Question 35

typedef struct node {
  int value;
  struct node * next;
}
Node;

Node * modify_list(Node * head) {

    Node * p, * q;
    if ((head == NULL || (head-> next == NULL)) 
    return head; 
    
    q = NULL; 
    p = head;
      while (p-> next-> next != NULL) {
        q = p;
        p = p -> next;
      }
      q -> next = p -> next; 
      p -> next = head; 
      head = p;
      
      return head;
    }