function isValidParentheses(expression: string): boolean {
  const mapping = {")": "(", "]": "[", "}": "{"}
  const stack = []

  for (const char of expression) {
    if (mapping[char]) {
      if (stack.length === 0 || stack[stack.length-1] !== mapping[char]) {
        return false
      }
      stack.pop()
    } else {
      stack.push(char)
    }
  }
  return stack.length === 0
}

// No modificar: necesario para evaluar el resultado.
export { isValidParentheses };