Rosetta Code Popular

Balanced Brackets

Check whether bracket pairs are properly nested and closed by scanning the text with a stack.

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Sourcerosettacode/popular/balanced_brackets.vibe
type RunResult = {
  crossed_false: bool,
  incomplete_false: bool,
  mixed_true: bool,
  nested_true: bool
}

def opener_for(char: string) -> string?
  if char == ")"
    "("
  elsif char == "]"
    "["
  elsif char == "}"
    "{"
  else
    nil
  end
end

def closer?(char: string) -> bool
  char == ")" || char == "]" || char == "}"
end

def balanced_brackets?(text: string) -> bool
  text_chars = text.chars
  stack: array<string> = []
  depth = 0
  index = 0

  while index < text.length
    char = text_chars.fetch(index)

    if char == "(" || char == "[" || char == "{"
      stack.push(char)
      depth = depth + 1
    elsif closer?(char)
      if depth == 0
        return false
      end

      top = stack.pop
      depth = depth - 1

      if top != opener_for(char)
        return false
      end
    end

    index = index + 1
  end

  depth == 0
end

def run -> RunResult
  {
    nested_true: balanced_brackets?("{[()()]}"),
    mixed_true: balanced_brackets?("function(x) { return [x, x + 1] }"),
    crossed_false: balanced_brackets?("([)]"),
    incomplete_false: balanced_brackets?("{[()}")
  }
end

Output

Click Run example to see the result.

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