The key idea behind using a stack is that it allows for easy access to the most recently added element and easy removal of that element, which can be useful in situations where you need to keep track of a history of actions or reverse actions. So based on various use cases, there are several applications of stack in coding problem solving and computer programming:
When we are browsing the web, the back and forward buttons on our web browser can be really handy for navigating between pages. We can implement these buttons by maintaining two separate stacks of links to web pages. The back stack contains links to pages we have previously visited, and the forward stack contains links to pages we have navigated away from but may want to revisit.
If we want to go back to a page we have previously visited, we can use the back button. This removes the current page from the top of the back stack, and stores it on the forward stack. If we want to move forward again, we can use the forward button, which retrieves the page from the top of the forward stack and pushes the current page onto the back stack. In this way, we can move back and forth through the pages we have visited without having to manually enter the URL of each page.
The UNDO/REDO functionality in text editors and image editing software can be implemented using a stack by using two separate stacks: one for undo and one for redo. Every time we perform an action on the document or image, a new record containing information about the action is created and added to the top of the undo stack.
If we choose to undo an action, the top record is removed from the undo stack and added to the redo stack, undoing the action in the document or image. Conversely, if we choose to redo an action, the top record is removed from the redo stack and added back to the undo stack, redoing the action in the document or image.
This is a common and efficient method to implement the undo/redo functionality, however, there are other methods that can be used such as using a more complex data structure like a linked list which allows for storing more data and the ability to go back multiple steps. Alternatively, we could save different versions of the document or image and switch between them.
A stack data structure can be used in systems where memory is allocated in a static way to manage memory allocation and track which memory blocks are in use. Additionally, it can be used to keep track of function calls in a program and ensure that the program returns to the correct location when a function is complete.
The Java Virtual Machine (JVM) uses this concept in keeping track of the state of a running Java program, it uses two types of stacks, the Java Stack and the Native Stack. The Java Stack stores the state of Java method invocations, creating and adding a new frame to the stack each time a method is invoked, it contains information about the method's local variables, the current line of execution, and the return address. The Native Stack is used for method invocations written in languages other than Java such as C or C++, and it interacts directly with the underlying operating system and hardware.
Delimiter checking is a process that verifies if a string of characters has matching pairs of delimiters, such as parentheses, brackets, and curly braces. One way of accomplishing this is by using a stack data structure and keeping track of the delimiters encountered while parsing the string. The process is as follows:
bool isBbalanced(string str)
{
stack<char> s;
for (int i = 0; i < str.length(); i = i + 1)
{
if (str[i] == '(' || str[i] == '[' || str[i] == '{')
s.push(str[i]);
else if (str[i] == ')' || str[i] == ']' || str[i] == '}')
{
if (s.empty() == true)
return false;
char top = s.top();
if ((top == '(' && str[i] == ')') || (top == '[' && str[i] == ']') || (top == '{' && str[i] == '}')) {
s.pop();
else
return false;
}
}
if(s.empty() == true;
return true;
else
return false;
}This approach works because when a closing delimiter is encountered, the most recent opening delimiter should correspond to it. If the delimiters match correctly, the opening and closing delimiters will be removed from the stack in the correct order. This is a simple way to implement delimiter checking, variations such as checking for specific delimiters with specific characteristics or ignoring certain delimiters in certain contexts are also possible.
Recursion is a technique where a function calls itself in order to solve a problem. To manage this, a call stack is used to keep track of the function calls and return points as the recursion takes place.
Each time a function is called, a new frame is added to the stack, which contains the function's local variables and return address. Once the base case is reached and the function returns a value, the corresponding frame is popped off the stack and the return value is passed up to the next level.
This process continues until the original call has returned the final value and all the frames have been popped off the stack. It's important to note that this is a simplified explanation and in practice, the process may differ, but the main concept remains the same. Additionally, some languages have tail-recursion optimization, which allows the compiler to optimize the recursion process.
Stacks are commonly used in the process of evaluating mathematical expressions written in infix notation (e.g., (1 + 2) * 3) by converting them to postfix notation (e.g., 1 2 + 3 * ). This process is known as expression conversion or evaluation, where the operators in-between operands (e.g. 1 + 2) are converted to postfix notation (e.g. 1 2 +) and then evaluated with the use of stack data structure.
Here are the general steps of this process:
This method works because postfix notation has the operator applied to the operands immediately before it, unlike infix notation where operator is in-between the operands. Stack keeps the track of the operands and operators during the conversion and evaluation process and thus ensures the correct order of operations in the postfix notation expression.
In web development, it's important to ensure that the opening and closing tags of an HTML document match correctly. This can be done using a stack data structure. The basic idea is to use a stack to keep track of the opening tags as they are encountered in the HTML document, and then match them with the corresponding closing tags as they are encountered. Here's a general overview of how this process works:
This approach works because when a closing tag is encountered, the most recent opening tag on the stack should correspond to it. If the tags match, the opening and closing tags are removed from the stack in the correct order. Additionally, stacks are used in some HTML parsing libraries to parse HTML and generate a tree-like structure. This method can provide more information about the structure of the HTML and can be useful for tasks such as creating a table of contents or modifying the style of specific elements on a page.
Enjoy learning, enjoy algorithms!