Introduction to Stack Data Structures
A stack is a data structure that stores items in a Last In First Out (LIFO) manner. It is a linear data structure that allows for the addition and removal of elements from the same end, commonly referred to as the top of the stack.
A stack can be implemented in either an array or a linked list. In an array-based implementation, the stack is represented as an array and the top of the stack is the last element of the array. In a linked list-based implementation, the stack is represented as a linked list and the top of the stack is the head node of the list.
A stack can be used for a variety of purposes such as storing data, solving algorithms, and implementing recursion. Stacks are also used in a variety of applications such as web browsers, operating systems, and compilers.
Stacks have two main operations: push and pop. Push adds an element to the top of the stack while pop removes the top element from the stack. Other operations that can be performed on a stack include peek, which returns the top element without removing it, and isEmpty, which returns a boolean indicating whether the stack is empty.
Stacks are an important data structure that is used in many applications and algorithms. They offer an easy and effective means of manipulating and storing data.
Implementation of Stack Data Structure in C++
stack<int> s; /* PUSHING ELEMENTS INTO STACK */ s.push(3); s.push(0); s.push(4); s.push(1); s.push(7); // stack is 3 0 4 1 7(top) cout<<"top element is "<<s.top(); //7 /* pop OPERATION IN STACK */ s.pop(); // 7 is poped, i.e Last in first out(LIFO) //Now top element is 1 cout<<"top "<<s.top(); cout<<"size of stack = "<<s.size(); // 4
Common Operations in Stack
- Operation PUSH
A push operation is when an element is added to the stack. The new element is inserted at the top of the stack since there is only one other location where it may be added: the top of the stack.
- Operation POP
Removal of an element is referred to as a pop operation. Again, since we can only access the element at the top of the stack, there is only one element that may be removed. Simply the top of the stack is removed. It is entirely up to the programmer to decide whether to implement the option to return the value of the element that was popped.
- Operation TOP
the user can see the element at the top of the stack. No changes are made to the stack during this process.
Determine whether the stack is empty.
To avoid performing operations on an empty stack, the programmer must internally monitor the size of the stack, which will be updated throughout push and pop operations. Usually, the boolean value returned by the function isEmpty() True if size equals 0, otherwise False.
Advantages of Using Stack Data Structures
- Fast Access: One of the main advantages of using a stack data structure is its fast access time. Stacks are based on the principle of Last-In-First-Out (LIFO), which allows for quick access to the most recently added element. This is useful for applications that require quick access to the most recent data, such as web browsers and operating systems.
- Memory Efficiency: Stacks are also very memory efficient due to their design. They only require the use of one pointer to keep track of the top of the stack, which makes them much more memory efficient than other data structures such as linked lists which require multiple pointers.
- Limited Operations: Stacks only allow for two basic operations; pushing and popping. They are therefore incredibly simple to comprehend and use. This also helps to ensure that the stack remains in a consistent state and can easily be manipulated.
- Recursion: Stacks are widely used in recursive algorithms. The stack is used to store the state of the function as it recurses, and when the function returns, the stack is used to restore the previous state. This makes recursive algorithms much easier to implement and understand.
- Error Handling: Stacks can also be used to help with error handling in programs. When an error occurs, the stack can be used to store the state of the program before the error occurred. This allows the program to be rolled back to the state before the error occurred and the error can be handled properly.
Applications of Stack Data Structures
Stack data structures are a type of data structure that relies on the Last In First Out (LIFO) principle. This means that when data is added to the stack, the most recently added item is the first one to be removed. A linear data structure known as a stack is useful in many different contexts. The following are some of the most common applications of stack data structures:
- Expression Evaluation and Syntax Parsing: Stacks are often used to evaluate expressions and parse syntax in various programming languages. This process involves pushing the tokens of the expression onto the stack as they are read. The expression is then evaluated by popping the tokens off the stack in reverse order and performing the necessary operations.
- Backtracking: Backtracking is a process of finding a solution to a problem by trying different combinations of values until a solution is found. It is often used in algorithms such as depth-first search and Dijkstra’s algorithm. Stacks are used to store the combination of values that have already been tried, so the algorithm can backtrack if necessary.
- Memory Management: Stacks are often used in memory management to store the address of the instructions that are currently being executed. This information is used by the processor to determine where it should jump to when an instruction is completed.
- Undo/Redo Operations: Stacks are used in many applications to allow users to undo/redo operations. When a user performs an operation, the details of that operation are pushed onto a stack. When the user wants to undo the operation, the details are popped off the stack and the operation is reversed.
- Recursion: Recursion is a process in which a function calls itself until a certain condition is met. Stacks are used to store the state of the function each time it is called, so the function can return to the correct state when the condition is met and the recursion ends.