valid-parentheses-worst.go

func hasForwardMatch(target string, index int) bool {
    matchStack := 1
    for i := index + 1; i < len(target); i++ {
        if target[i] == '(' {
            matchStack++
        } else {
            matchStack--
            if matchStack == 0 {
                return true
            }
        }
    }
    return matchStack == 0
}

func hasBackwardMatch(target string, index int) bool {
    matchStack := 1
    for i := index - 1; i > -1; i-- {
        if target[i] == ')' {
            matchStack++
        } else {
            matchStack--
            if matchStack == 0 {
                return true
            }
        }
    }
    return matchStack == 0
}

func ValidParentheses(parens string) bool {

    if len(parens) == 1 { return false }

    recChan := make(chan bool)
    numRoutines := 0

    for i := range parens {
        numRoutines++
        if parens[i] == '(' {
            go func(i int) {
                recChan <- hasForwardMatch(parens, i)
            }(i)
        } else {
            go func(i int) {
                recChan <- hasBackwardMatch(parens, i)
            }(i)
        }
}

  for i := 0; i < numRoutines; i++ {
    if valid := <-recChan; !valid {
      return false
    }
  }

  return true
}