When Should We Use Stack Data Structure?

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Larry Thompson

When Should We Use Stack Data Structure?

A stack is a fundamental data structure in computer science that follows the Last-In-First-Out (LIFO) principle. It is like a stack of plates where the last plate placed on top is the first one to be removed.

This unique characteristic makes the stack data structure useful in various scenarios. In this article, we will explore when and why we should use a stack.

1. Reversing Order

Stacks can be used to reverse the order of elements efficiently.

By pushing elements onto a stack and then popping them off, we can obtain the reversed order of the original sequence. This operation is particularly useful when dealing with strings, arrays, or linked lists.

2. Undo/Redo Operations

Stacks are often employed to implement undo/redo functionality in applications such as text editors or graphic design software.

Each action taken by the user is stored as a command object and pushed onto a stack. When an undo operation is triggered, the most recent command is popped from the stack and executed in reverse order.

3. Balancing Symbols

Stacks come in handy when checking for balanced symbols such as parentheses, braces, or brackets in an expression.

As we encounter opening symbols, they are pushed onto the stack. If a closing symbol is found, it must match with the top element of the stack before being popped off.

Example:

function checkBalancedSymbols(expression) {
  let stack = [];
  for (let char of expression) {
    if (isOpenSymbol(char)) {
      stack.push(char);
    } else if (isCloseSymbol(char)) {
      if (stack.length === 0 || !isMatchingPair(stack.pop(), char)) {
        return false;
      }
    }
  }
  return stack.length === 0;
}

4. Function Call Stack

Stacks are extensively used in programming languages to keep track of function calls and their local variables.

Each time a function is called, a new frame is added to the stack. When the function completes its execution, its frame is removed from the stack. This mechanism allows for proper handling of nested function calls.

5. Parsing and Evaluation

Stacks are commonly employed in parsing and evaluating expressions, particularly in infix, postfix, and prefix notations. They can be used to convert an expression from one notation to another or to evaluate arithmetic or logical expressions step by step.

Example:

function evaluatePostfixExpression(expression) {
  let stack = [];
  for (let token of expression) {
    if (isOperand(token)) {
      stack.push(token);
    } else if (isOperator(token)) {
      let operand2 = stack.pop();
      let operand1 = stack.pop();
      let result = performOperation(operand1, token, operand2);
      stack.push(result);
    }
  }
  return stack.pop();
}

In conclusion, stacks are versatile data structures that find applications in a wide range of domains. Whether it’s reversing order, implementing undo/redo functionality, checking symbol balance, managing function calls, or parsing and evaluating expressions – stacks provide an elegant solution.

By understanding when and why to use stacks in different scenarios, you can leverage their power to improve the efficiency and functionality of your programs.

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