How to check validity of closed brackets, parentheses or brackets in Ruby

Question

Write a method 'valid_string?' that accepts a string. It returns true if the brackets, parentheses, and curly braces close correctly. It returns false otherwise.

valid_string?("[ ]")                  # returns true
valid_string?("[  ")                  # returns false
valid_string?("[ ( text ) {} ]")      # returns true
valid_string?("[ ( text { ) } ]")     # returns false

---

My code: Is returning false for everything. Even tried using explicit booleans for individual cases {} || () ||, etc. Did not work. Either returns true or false for everything. Is it my driver code?

def valid_string?(str) 

    if str == ("\[\s+]")
        true
    else
        false
    end
end

UPDATED SOLUTION:------------------------------------------------ Yes! #match definitely worked out better! Although my last line of test code is evaluating to true. When it should be false. . .

def valid_string?(str) 
if str.match "(\\[.+\\])" || "|(\\(\\))" || "|({})"
    return true
else
    return false
    end
end

puts valid_string?("[ ]")                  # returns true
puts valid_string?("[  ")                  # returns false
puts valid_string?("[ ( text ) {} ]")      # returns true
puts valid_string?("[ ( text { ) } ]")     # returns false

Answer 1

How about a simple counting routine?

def valid_string?(str)
  match_count = 0

  str.each_char do |c|
    match_count += 1 if [ '[', '{', '(' ].include?(c)
    match_count -= 1 if [ ']', '}', ')' ].include?(c)
  end

  return match_count == 0
end

Answer 2

I think it might be complicated to use regex to solve this problem. Here is a potential solution: You may use a stack to record the left symbol like {, [, ( in the traverse. Each time you met the right symbol, just check whether the symbol on the stack top matches this right symbol. Simply return false if not match.

Below is my code:

def valid_string?(str)
  stack = []
  symbols = { '{' => '}', '[' => ']', '(' => ')' }
  str.each_char do |c|
    stack << c if symbols.key?(c)
    return false if symbols.key(c) && symbols.key(c) != stack.pop
  end
  stack.empty?
end

puts valid_string?('[ ]')                  # returns true
puts valid_string?('[  ')                  # returns false
puts valid_string?('[ ( text ) {} ]')      # returns true
puts valid_string?('[ ( text { ) } ]')     # returns false