Stack datastructure

 

𝗦𝘁𝗮𝗰𝗸 𝗗𝗮𝘁𝗮 𝗦𝘁𝗿𝘂𝗰𝘁𝘂𝗿𝗲 :

A stack is a linear data structure that follows the principle of Last In First Out (LIFO). This means the last element inserted inside the stack is removed first.

A stack is a linear data structure that follows the principle of Last In First Out (LIFO). This means the last element inserted inside the stack is removed first.

You can think of the stack data structure as the pile of plates on top of another.

Here, you can:

• Put a new plate on top
• Remove the top plate

And, if you want the plate at the bottom, you must first remove all the plates on top. This is exactly how the stack data structure works.

𝗟𝗜𝗙𝗢 𝗣𝗿𝗶𝗻𝗰𝗶𝗽𝗹𝗲 𝗼𝗳 𝗦𝘁𝗮𝗰𝗸 :

In programming terms, putting an item on top of the stack is called push and removing an item is called pop.

We can implement a stack in any programming language like C, C++, Java, Python or C#, but the specification is pretty much the same.

𝗕𝗮𝘀𝗶𝗰 𝗼𝗽𝗲𝗿𝗮𝘁𝗶𝗼𝗻𝘀 𝗼𝗳 𝘀𝘁𝗮𝗰𝗸 :

There are some basic operations that allow us to perform different actions on a stack.

Push: Add an element to the top of a stack

Pop: Remove an element from the top of a stack

IsEmpty: Check if the stack is empty

IsFull: Check if the stack is full

Peek: Get the value of the top element without removing it

𝗪𝗼𝗿𝗸𝗶𝗻𝗴 𝗼𝗳 𝗦𝘁𝗮𝗰𝗸 𝗗𝗮𝘁𝗮 𝗦𝘁𝗿𝘂𝗰𝘁𝘂𝗿𝗲 :

The operations work as follows:

1. A pointer called TOP is used to keep track of the top element in the stack.
2. When initializing the stack, we set its value to -1 so that we can check if the stack is empty by comparing TOP == -1.
3. On pushing an element, we increase the value of TOP and place the new element in the position pointed to by TOP.
4. On popping an element, we return the element pointed to by TOP and reduce its value.
5. Before pushing, we check if the stack is already full
6. Before popping, we check if the stack is already empty. 

𝗦𝘁𝗮𝗰𝗸 𝗧𝗶𝗺𝗲 𝗖𝗼𝗺𝗽𝗹𝗲𝘅𝗶𝘁𝘆 :

For the array-based implementation of a stack, the push and pop operations take constant time, i.e. O(1).

𝗔𝗽𝗽𝗹𝗶𝗰𝗮𝘁𝗶𝗼𝗻𝘀 𝗼𝗳 𝗦𝘁𝗮𝗰𝗸 𝗗𝗮𝘁𝗮 𝗦𝘁𝗿𝘂𝗰𝘁𝘂𝗿𝗲 :

Although stack is a simple data structure to implement, it is very powerful. The most common uses of a stack are:

• To reverse a word - Put all the letters in a stack and pop them out. Because of the LIFO order of stack, you will get the letters in reverse order.

• In compilers - Compilers use the stack to calculate the value of expressions like 2 + 4 / 5 * (7 - 9) by converting the expression to prefix or postfix form.

• In browsers - The back button in a browser saves all the URLs you have visited previously in a stack. Each time you visit a new page, it is added on top of the stack. When you press the back button, the current URL is removed from the stack, and the previous URL is accessed.