- Use the
Stack
implementation we built in the previous lab to solve a problem - Write an algorithm to check whether the parentheses in a string are balanced
In this lab, you'll use the Stack
class you built in the previous lab to write
an algorithm that takes a string as input and checks to see whether the
parentheses in the string are balanced.
A single pair of parentheses is defined as balanced if it consists of an opening
parenthesis followed by a matching closing parenthesis. A string containing some
number of (
and )
characters will be considered balanced if it includes only
balanced pairs:
- Balanced:
()
,(()())
- Not balanced:
())()
,)
You will be using the Stack
implementation we developed in an earlier lesson
to help you solve this lab. We have included the code in lib/stack.rb
. We have
also required that file in lib/balancing_parentheses.rb
, where you will be
coding your solution.
Write a balancing_parentheses
method in the lib/balancing_parentheses.rb
file that:
- Takes as input a string consisting of some number of
(
and)
characters - Creates an instance of the
Stack
class - Using the stack, checks the string to determine whether the parentheses inside it are balanced
- Returns the number of additional parentheses that would need to be added to the string to make it balanced
Here are some examples of the expected return value for your method for various inputs:
Input: `()`
Output: 0
Input: `())()`
Output: 1
Input: `(()()(()`
Output: 2
Note: There are a number of ways to solve this problem, but for this lab you
need to use a stack (specifically, an instance of our Stack
class) in the
solution.