It is always interesting to learn about the
applications of Data
Structures and Algorithms in our daily lives. One such application
is Stack. We’ll now take a detailed look into Stacks.
What is
a Stack?
A stack is an Abstract Data Type (ADT) that is
commonly used in most programming languages. It gets its name from the way it
behaves like a real-world stack, for example a deck of cards or a pile of
plates. If we want to add or remove something from a stack, we can only do so
from the top. For example, we can only place or remove a card or plate from the
top of the stack. Likewise, the Stack ADT only allows all data operations at
one end. At any given time, the only element we can access in a stack is the
top element.
This feature makes it a LIFO data structure.
LIFO stands for Last-in-first-out. Here, the element which is placed last is
accessed first. There are several ways to implement a stack, including using an
array, a structure, a pointer, or a linked list. A stack can be a fixed size or
it may be dynamically resized.
An algorithm must have some operations to be
performed. The following are the operations of Stack:
i) Push
ii) Pop
iii) Peek
iv) isEmpty
v) Size
i) Push
The adding of elements into the stack is known
as Push operation.
ii) Pop
The removal of elements from the stack is
known as Pop operation.
iii)
Peek
The return of the top most value of the stack
without having it removed from the stack.
iv) isEmpty
Checking for a stack if it is empty or not.
v) Size
At any given time, a stack will have a certain
number of elements in it. This number can be determined by using a function.
Stack can be applied in a variety of
applications. There are various conversion applications such as, conversion of
Infix to Postfix, Infix to Prefix, and so on. One such application is the
conversion of Infix to Prefix notation.
What is
an Infix notation?
We’ll now look into what an Infix expression
is.
Infix notation is a way of writing expressions
in which the operators are placed between the operands. For example, in the
expression A+B, the + symbol is an operator between the operands A and B. Other
examples of infix notation include A*B and A/B. Since the operators are placed
in between the operands, this is called an Infix expression.
What is
a Prefix notation?
In this notation, the operator is written
before the operands. For example, +ab is equivalent to the infix notation a +
b. This notation is known as Prefix Notation.
Conversion
of Infix to Prefix:
The compiler will scan the given expression
from either left to right, or from right to left.
i) First, reverse the given infix expression.
ii) Then, scan the characters one by one.
iii) If the character is an operand, copy it
to the prefix notation output.
iv) If the character is a closing parenthesis,
push it to the stack.
v) If the character is an opening parenthesis,
pop the elements in the stack until the corresponding closing parenthesis is
found.
vi) If the character scanned is an operator,
we'll check to see if it has precedence greater than or equal to the top of the
stack.
vii) If it does, we'll push the operator to
the stack.
viii) If the operator has lower precedence
than the top of the stack, we'll pop the operator and output it to the prefix
notation output.
ix) Then, we'll check the condition again with
the new top of the stack.
x) After scanning all the characters, reverse
the prefix notation output.
We’ll now look into the advantages and
disadvantages of Stacks
Advantages
of Stacks:
i) If you're looking for a way to manage data
using the LIFO technique, stack is a great option.
ii) Stacks are also helpful for systematic
memory management, and can be found in many virtual machines like JVM.
iii) One of the advantages of stack is that
it's very efficient for function management since local variables and function
parameters are stored in the stack and automatically destroyed once the
function is returned.
iv) Additionally, stacks are more secure and
reliable as they don't get corrupted easily.
v) Stack gives you control over memory
allocation and deallocation. Stack automatically cleans up the objects for you.
Disadvantages
of Stacks:
i) Stack memory is relatively small.
ii) The total size of the stack must be defined
in advance.
iii) If too many objects are created, it can
lead to stack overflow.
iv) Random access is not possible in a stack.
v) If the stack falls outside of memory, it
can lead to abnormal termination.
Conclusion
In this article, we have discussed Stack, and
one of its applications. The application that is discussed is the conversion of
an expression from an Infix notation to a Prefix notation. Stack is an
important concept in Data science course in Mangalore. Stacks can be useful for keeping track of previous steps in a
process. For example, parsing questions often uses stacks because of the LIFO
(last in, first out) property. Stacks can also be used to implement recursive
solutions iteratively. This means that instead of having the function call
itself repeatedly, the function can keep track of what it needs to do next on a
stack. Since Stacks are a prominent concept of Data Structures and Algorithms,
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