iit bombay x

Question

A struct Node(shown below) is used to implement a linked list.

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

The function a_function (shown below), takes the head (i.e. the first element of the list), as argument, and reorders the list.The swap function inside the function, swaps the 2 elements of the list, which are passed to it as arguments

void a_function (Node* head) {
  Node* a_ptr = head;
  bool val = true;
  while (a_ptr->next != NULL) {
    if (val)  {
        if (a_ptr->data > a_ptr->next->data)
            swap(a_ptr->data, a_ptr->next->data);
    }
    else {
        if (a_ptr->data < a_ptr->next->data)  {
            swap(a_ptr->data, a_ptr->next->data);
        }
    a_ptr = a_ptr->next;
    val = !val;
    }
  }
}

Choose all options, that are correct about the above function a_function

a>The function,a_function, sorts the linked lest in ascending order., 

b>The function, a_function, rearranges the list in zigzag fashion (i.e. a,b,c,d,e,f... be the data in the list after the list is rearranged, then the list is of the form a < b > c < d > e < f...)

c>Given a list 4, 3, 7, 8, 6, 2, 1. The function, a_function, rearranges it to 3, 7, 4, 8, 2, 6, 1.

d>Given a list 11, 15, 20, 16, 21, 23, 17. The function, a_function, rearranges it to 11, 15, 16, 17, 20, 21, 23.

Answer 1

ans would be C. 4 3 7 8 6 2 1

val=1, a_ptr at 4,  first two element has been swapped : 3 4 7 8 6 2 1

val=0, a_ptr at 4 in updated list ,so 4 and 7 is swapped : 3 7 4 8 6 2 1

val=1,a_ptr at 4 in updated list, but condition failed : 3 7 4 8 6 2 1

val=0 , a_ptr at 8 in updated list, but condition failed : 3 7 4 8 6 2 1

val=1,a_ptr at 6 in updated list  , so 6 and 2 is swapped: 3 7 4 8 2 6 1

val=0,a_ptr at 6 in updated list , but condition failed : 3 7 4 8 2 6 1

val=1 , a_ptr at 1 in updated list but while loop condition fails

so 3 7 4 8 2 6 1 is final ans:

plz correct me...

Comments

you are correct but option b is also correct...nd very nice explanation ... explanation given:

The function swaps the elements in alternating ascending and descending order (zigzag like order), such that, if a, b,c,d,e,f,.. are the elements in the list, then the form of the list is a < b > c < d > e < f...

Answer 2

As told in question more than one options may be correct.

Here Option B & C are Correct.

How to Approach this Question:-

Step1:- Read all options

Step2:- Directly apply Option C's example into given Code.
and Option C is Correct  so Option A is wrong now verify Option B.

Result of Option C satisfies Option B as shown below

3 < 7 > 4 < 8 > 2< 6 > 1

Step3:- Now Apply Option 4 in Code

We get resultant list as below

11 < 20 > 15 < 21> 16< 23> 17

So option D is incorrect But it

Satisfies Option B.

 So option B & C are Correct.