Understanding Stack Operations and Implementations in Programming

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A stack is a fundamental data structure in programming that follows the Last In, First Out (LIFO) principle. This means that the last element added to the stack is the first one to be removed. Here’s a detailed explanation of how a stack works, including its operations and applications:

Basic Operations of a Stack

1. Push Operation:
   • Purpose: Adds an element to the top of the stack.
   • Steps:
     1. Check if the stack is full.
     2. If not full, increment the top pointer.
     3. Insert the new element at the position pointed to by the top pointer.
   • Example: If you have a stack with elements [10, 20, 30] and you push 40, the stack becomes [10, 20, 30, 40].

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2. Pop Operation:
   • Purpose: Removes the top element from the stack.
   • Steps:
     1. Check if the stack is empty.
     2. If not empty, access the top element.
     3. Decrement the top pointer.
   • Example: If you have a stack with elements [10, 20, 30] and you pop an element, the stack becomes [10, 20] and the popped element is 30.

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3. Peek Operation:
   • Purpose: Retrieves the top element of the stack without removing it.
   • Steps:
     1. Check if the stack is empty.
     2. If not empty, return the element at the top position.
   • Example: If you have a stack with elements [10, 20, 30], peeking returns 30 without altering the stack.

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4. isEmpty Operation:
   • Purpose: Checks if the stack is empty.
   • Steps:
     1. Check if the top pointer is less than 1 (or -1 in some implementations).
     2. Return true if empty, false otherwise.
   • Example: If you have an empty stack, isEmpty() returns true.
5. isFull Operation:
   • Purpose: Checks if the stack is full.
   • Steps:
     1. Check if the top pointer equals the maximum size of the stack.
     2. Return true if full, false otherwise.
   • Example: If you have a stack with a maximum size of 5 and it contains 5 elements, isFull() returns true.

Implementation of a Stack

Stacks can be implemented using different data structures such as arrays or linked lists:

1. Array-Based Implementation:
   • Advantages: Simple and efficient for small stacks.
   • Disadvantages: Fixed size, potential for overflow if the stack size exceeds the array capacity.
   • Example in C:

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     #include <stdio.h>
     #define SIZE 4
     int top = -1, inp_array[SIZE];
     void push() { /* implementation */ }
     void pop() { /* implementation */ }
     

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