Applications of Stacks

Stacks are widely used in computer science due to their ability to efficiently manage data in a Last-In-First-Out (LIFO) manner. Let's explore some common real-world applications of stacks:

• Function Call Stack: Stacks are essential in programming languages for managing function calls. Whenever a function is called, a new frame is pushed onto the stack, which contains information about the function's local variables and return address. This allows functions to execute and return in the correct order.
• Expression Evaluation: Stacks are often used to evaluate arithmetic expressions. For example, the expression 5 10 + 3 * can be evaluated using a stack-based calculator algorithm. Here's an example in Java:

1<<code>>

• Browser History: Many web browsers use a stack to implement the Back and Forward buttons. Each time you visit a new page, it is pushed onto the stack. When you click the Back button, the previous page is popped from the stack and displayed.

• Undo/Redo: Stacks are commonly used to implement undo/redo functionality. Each action performed by the user is stored as a command object and pushed onto the stack. When the user performs the undo operation, the top command is popped from the stack and reversed. The redo operation can then reapply the command by pushing it back onto the stack.

• Balanced Parentheses: Stacks are essential for checking the validity of parentheses in programming languages. A stack can be used to keep track of opening and closing parentheses. When an opening parenthesis is encountered, it is pushed onto the stack. When a closing parenthesis is encountered, the stack's top element is checked to ensure it matches the closing parenthesis.

• Backtracking Algorithms: Backtracking algorithms, such as depth-first search, heavily rely on stacks to store state information during the search process. Each time a decision is made, the current state is pushed onto the stack. If the search reaches a dead end, the top state is popped from the stack to backtrack and explore alternative paths.

These are just a few examples of how stacks are used in computer science. Their simplicity and efficiency make them a powerful tool for solving a wide range of problems.

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}

class Main {

  public static void main(String[] args) {

    // replace with your Java logic here

    System.out.println("Implementing a stack-based calculator:");

​

    String expression = "5 10 + 3 *";

    double result = evaluate(expression);

​

    System.out.println("Result: " + result);

  }

​

  static double evaluate(String expression) {

    Stack<Double> stack = new Stack<>();

    String[] tokens = expression.split(" ");

​

    for (String token : tokens) {

      if (isNumber(token)) {

        stack.push(Double.parseDouble(token));

      } else {

        double operand2 = stack.pop();

        double operand1 = stack.pop();

        double result = 0;

​

        switch(token) {

          case "+":

            result = operand1 + operand2;

            break;

          case "-":

            result = operand1 - operand2;