Page 47 - Data Structures Interactive Book

5.3 Operations on Stacks

The operations on stacks define how this data structure behaves and ensure that it

follows the Last-In, First-Out (LIFO) principle. Each operation manipulates the stack in a
specific way and understanding them is essential for applying stacks in practical scenarios

such as expression evaluation or recursion.

5.3.1 Push Operation

The push operation adds a new element to the top of the stack. In an array-based

implementation, this involves incrementing the top index and storing the new value at that

position. In a linked list implementation, a new node is created and linked to the existing top

node. If the stack is already full (in arrays), an overflow occurs, which must be handled to

prevent errors. Push is fundamental because it builds the stack structure step by step.

5.3.2 Pop Operation

The pop operation removes the element currently at the top of the stack. In arrays,

this means decrementing the top index, while in linked lists it involves deleting the top node

and updating the pointer to the next node. If the stack is empty, a stack underflow occurs,
which is an error condition. Pop is crucial for reversing actions or retrieving the most recent

data stored.

5.3.3 Peek/Top Operation

The peek (or top) operation allows the programmer to view the element at the top of
the stack without removing it. This is useful for checking the current state of the stack, such

as when evaluating mathematical expressions or verifying balanced symbols. Peek provides

insight into the stack’s contents while preserving its structure.

5.3.4 Checking for Empty and Full Conditions

Before performing push or pop, it is important to check whether the stack is empty or

full. In arrays, the stack is full when top == MAX-1 and empty when top == -1. In linked lists,

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