type Solution struct{}

func (s *Solution) isValid(str string) bool {
  par := map[byte]byte{
    '[': ']',
    '(': ')',
    '{': '}',
  }

  stack := []byte{}

  for i := 0; i < len(str); i++ {
    curr := str[i]

    if v, ok := par[curr]; ok {
      // if curr is opening push its closing to stack
      stack = append(stack, v)
    } else if len(stack) != 0 && curr == stack[len(stack)-1] {
      // otherwise curr should be correct closing - so pop it from stack
      stack = stack[:len(stack)-1]
    } else {
      // in that case curr is incorrect closing
      return false
    }
  }
  
  return len(stack) == 0
}