Solved: java stack char

Stacks are a fundamental data structure in computer science, allowing for efficient operations and storage. In Java, a stack of characters can be particularly useful in solving specific programming problems such as string manipulation, parsing, and syntax analysis. In this article, we will see how to create and work with a stack of characters in Java, while also exploring related libraries and functions that facilitate problem-solving with character stacks.

A stack is a Last In, First Out (LIFO) data structure, which means that the last item added to the stack will be the first one to be removed. This behavior is useful in many programming contexts, such as matching parentheses, evaluating expressions, or even tracing the call stack of a program. Let’s delve into the implementation and usage of a character stack in Java.

Creating a Stack of Characters

In Java, the Stack class provided by the java.util package can be used for creating a stack of characters. Here is a simple example of how to declare a stack of characters and perform basic operations like pushing, popping, and peeking:

import java.util.Stack;

public class CharStack {
    public static void main(String[] args) {
        Stack<Character> stack = new Stack<>();

        // Push characters onto the stack
        stack.push('A');
        stack.push('B');
        stack.push('C');

        // Pop and peek characters from the stack
        System.out.println(stack.pop());
        System.out.println(stack.peek());
    }
}

Using a Character Stack to Solve Problems

Character stacks are particularly useful for solving problems that involve string manipulation or require tracking of nested elements. As an example, consider the problem of checking whether a given string of parentheses is balanced.

A string is considered balanced if:

• Every opening parenthesis has a corresponding closing parenthesis
• The pairs of parentheses are properly nested

We can use a character stack to efficiently solve this problem with the following steps:

1. Initialize an empty stack of characters
2. Loop through each character in the input string
3. If the character is an opening parenthesis, push it onto the stack
4. If the character is a closing parenthesis, check if the stack is empty and pop the top element if it is the corresponding opening parenthesis
5. If the stack is not empty after processing all characters, the string is unbalanced

Here’s the Java code for the above procedure:

public static boolean isBalanced(String input) {
    Stack<Character> stack = new Stack<>();

    for (char c : input.toCharArray()) {
        if (c == '(' || c == '{' || c == '[') {
            stack.push(c);
        } else if (c == ')' || c == '}' || c == ']') {
            if (stack.isEmpty()) {
                return false;
            }

            char top = stack.pop();
            if ((c == ')' && top != '(') || (c == '}' && top != '{') || (c == ']' && top != '[')) {
                return false;
            }
        }
    }

    return stack.isEmpty();
}

By understanding and utilizing stack data structure, we can effectively solve complex programming problems such as the ones involving string manipulation, parsing, and syntax analysis. Moreover, with the Stack class available in the java.util package, implementing and using character stacks in Java becomes a convenient endeavor.