Stack – A Comprehensive Introduction
In computer science, a stack is an abstract data type that holds a group of items that may only be added to or removed from the top of the stack. The Last-In-First-Out (LIFO) principle, which states that the last piece added to the stack will be the first one withdrawn, governs this situation. Push, which adds an element to the top of the stack, and pop, which removes the top element from the stack, are the two operations that the stack uses. Additional actions include isEmpty, which determines whether the stack is empty, and peek, which retrieves the value of the top element without deleting it. Stacks are frequently used in operating systems, programming languages, compilers, and other computer science disciplines.
Operations on Stack
Basic stack operations include:
Push: Adding an element to the stack’s top with this action.
The push action in a stack moves an element to the top of the stack. By allocating memory for the new element and then adding it to the top of the stack, this action is carried out. Any existing elements below the new element are pushed down one position, making it the new top of the stack.
Take a stack, for instance, initially it is empty. On pushing 11, element 11 will sit at the bottom of the stack. The stack pointer is initially -1, it points at index 0 now. On pushing 22, the top inter will point to index 1, and 22 will sit on top of 11. Similarly, we push item 33. The stack now has the values 44, 33, 22, and 1 in that sequence after we push the value 44 onto it, making it the new top element.
Pop: With this command, the top element in the stack is removed.
The pop operation in a stack eliminates the top member from the stack. The top element’s value is accessed, it is removed from the stack, and then the memory corresponding to that element is deallocated.
Take a stack, for instance, that has the components 44, 33, 22, and 11 in that sequence. When the top element, which is currently 44 on the stack, is removed, the new top element is 33 instead. 33, 22, and 11 are found in that sequence in the resulting stack. On the next pop(), item 33 is removed from the stack. Subsequent pop() calls will remove the top item every time. It is not possible to pop elements from an empty stack. So popping an empty stack should display an appropriate error message.
Peek (or Top): This operation returns the top element’s value while leaving it in place.
The peek (or top) operation in a stack retrieves the value of the top element without deleting it. Without changing the stack, this operation is completed by directly accessing the top element’s value.
Consider a stack, for instance, that has items 33, 22, and 11 in that specific order. The value 33, which represents the stack’s top element, will be returned if we use the peek operation on the stack. The stack is still filled with 33, 22, and 11 in that order after the peek operation, though.
isEmpty: This command determines whether the stack is empty.
The isEmpty operation in a stack determines whether the stack is empty, that is, devoid of elements. The top pointer, which is set to null or an empty value when the stack is empty, is used to conduct this action.
Think of a stack, for instance, that starts out empty. The stack is empty, thus if we run the isEmpty function on it, the result will be true. The isEmpty action will, however, return false if we push one element onto the stack because the stack now has one or more elements.
The stack’s contents can be adjusted using these operations. The push action increases the size of the stack by one by adding an element to the top. The stack’s size is decreased by one with the pop operation by removing the top element. In order to inspect the stack, the peek operation retrieves the value of the top element without removing it. To make sure you don’t try to pop an element from an empty stack, you can use the isEmpty operation to determine whether the stack is empty. Stack manipulation is built on these four fundamental actions, which are applied in a wide range of algorithms and programmes.
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