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

Consider the following C function takes a singly-linked list as input argument.

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;
    }

It modifies the list
(A) by moving the last element to the front of the list and returns the modified list.
(B) by moving the second last element to the front of the list and returns the modified list.
(C) by moving the first element to the second last of the list and returns the modified list.
(D) by moving the first element to the last of the list and returns the modified list.

Answer: (B)
Explanation: Function modify_list(Node * head) modifies the list by moving the second last element to the front of the list and returns the modified list.

Option (B) is correct.
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