List of top Computer Science and IT Engineering Questions on Data Structures asked in GATE CS

Consider a stack 𝑆 and a queue 𝑄. Both of them are initially empty and have the
capacity to store ten elements each. The elements 1, 2, 3, 4, and 5 arrive one by one,
in that order. When an element arrives, it is assigned either to 𝑆 (pushed on 𝑆 ) or
to 𝑄 (enqueued to 𝑄). Once all the five elements are stored, the output is generated
in two steps. First, stack S is emptied by popping all elements. Then queue 𝑄 is
emptied by dequeueing all elements. The output obtained by following this process
is 4 3 1 2 5 .
Given the output, the objective is to predict whether an element was assigned to 𝑆
or 𝑄.
Which of the following options is/are possible valid assignment(s) of the
elements?
Note: In the options, the notation 𝑥𝑆 denotes that element 𝑥 was assigned to 𝑆 and
𝑦𝑄 denotes that element 𝑦 was assigned to 𝑄.

Consider the following code snippet in C language that computes the number of
nodes in a non-empty singly linked list pointed to by the pointer variable head.
struct node{
int elt;
struct node *next;
};
int getListSize (struct node *head)
{
if( E1 ) return 1;
return E2;
}
Which one of the following options gives the correct replacements for the
expressions E1 and E2?