Data Structures and Algorithms

Stacks are used for postfix expression evaluation because operators are applied to the most recent operands, matching the LIFO (Last In First Out) principle. When encountering an operator, pop required operands from the stack, apply the operation, and push the result back.

The stack insertion operation (push) adds a new node to the top of the stack. The description matches this exactly: create a node, store the element, and insert at the top (the only insertion point in a stack).

Pre-order traversal visits the root node first, then recursively traverses the left subtree, then the right subtree. The 'pre' prefix means the root comes before (pre) its children.

AVL trees are self-balancing binary search trees where each node's balance factor (height of left subtree minus height of right subtree) must be -1, 0, or 1. This constraint ensures the tree remains balanced.

Linked lists are linear data structures where elements are arranged sequentially. Each node points to the next, forming a linear chain. Trees and graphs are non-linear as elements branch in multiple directions.

In queue implementation using arrays, FRONT=REAR indicates an empty queue. This is the initial state after initialization. When FRONT=REAR+1 (in circular queues), the queue is full.

Stack is not a static data structure.

Traversing is the correct answer.

This is the right answer.

In the worst case,  O(n2)In average case O(nlogn).

This is the limitation of binary search.

This is not a valid operation.

This is correct.

This is the right choice.