What Is Balanced Parentheses in Data Structure?


Larry Thompson

What Is Balanced Parentheses in Data Structure?

In the world of data structures, balanced parentheses play a crucial role in maintaining order and ensuring the correct execution of algorithms. Understanding what balanced parentheses are and how they work is essential for any programmer or computer science enthusiast.


Balanced parentheses refer to a situation where all opening parentheses have a corresponding closing parenthesis in the correct order. This means that for every opening parenthesis, there must be a closing parenthesis that matches it, and they must be properly nested.

A common example of balanced parentheses is mathematical expressions. In an expression like “(3 + 5) * (7 – 2)”, each opening parenthesis “(” has a corresponding closing parenthesis “)” in the correct order.


The concept of balanced parentheses is vital in many areas of computer science, particularly in parsing algorithms, which involve analyzing and processing strings of characters.

One significant application is expression evaluation. When evaluating an expression, such as “3 + 5 * (7 – 2)”, it’s crucial to ensure that the parentheses are balanced. This ensures that the arithmetic operations are performed correctly according to mathematical rules.

Detecting Balanced Parentheses

It’s often necessary to determine whether a given string of parentheses is balanced or not. Several algorithms can be used to accomplish this task.

Stack-Based Algorithm

  • Create an empty stack to store opening parentheses.
  • Iterate through each character in the string:
    • If the character is an opening parenthesis, push it onto the stack.
    • If the character is a closing parenthesis:
      • If the stack is empty, the parentheses are unbalanced.
      • If the stack is not empty, pop the top element from the stack.
      • If the popped element does not match the current closing parenthesis, the parentheses are unbalanced.
  • After iterating through all characters, if the stack is not empty, the parentheses are unbalanced.
  • If all opening parentheses have been matched and removed from the stack, and the stack is empty, then the parentheses are balanced.

This algorithm leverages a stack data structure to keep track of opening parentheses. If a closing parenthesis is encountered, it checks whether it matches with the last opening parenthesis that was pushed onto the stack.

If they match, they are considered balanced and removed from the stack. Otherwise, they are unbalanced.


Understanding balanced parentheses is crucial for various applications in computer science. Whether you’re evaluating expressions or designing parsing algorithms, ensuring that parentheses are properly balanced is essential for accurate results.

By following algorithms like the stack-based approach mentioned above, you can confidently handle and manipulate strings containing parentheses in your programming projects.


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