Code Spitz 90 - 코틀린 언어편 (1) 과제

code_spitz_90_1.kt

val trim = """[^.\d-+*/()]""".toRegex()
fun trim(v: String): String =  v.replace(trim, "")
fun repMMtoP(v: String) = v.replace("--", "+")
fun repMtoPM(v: String) = v.replace("-", "+-")
val groupMD = """((?:\+|\+-)?[.\d]+)([*/])((?:\+|\+-)?[.\d]+)""".toRegex()

tailrec fun removeMultiDiv(v: String): String = groupMD.find(v).let {
    if (it != null) {
        val (target, left, op, right) = it.groupValues
        val leftValue = left.replace("+", "").toDouble()
        val rightValue = right.replace("+", "").toDouble()
        val result = when (op) {
            "*" -> leftValue * rightValue
            "/" -> leftValue / rightValue
            else -> throw Throwable("invalid operator $op")
        }
        removeMultiDiv(v.replace(target, "+$result"))
    } else v
}

fun calcWithBracket(v: String): Double {
    return v
        .let { v.drop(1).dropLast(1) }
        .let { trim(it) }
        .let { repMMtoP(it) }
        .let { repMtoPM(it) }
        .let { removeMultiDiv(it) }
        .split("""(\++)""".toRegex())
        .fold(0.0) { accu, curr ->
            if (curr.isBlank()) { accu } else accu + curr.toDouble()
        }
}

tailrec fun removeBracket(v: String): String {
    return """\([.\d+\-*/]+\)""".toRegex().findAll(v).let {
        if (it.count() == 0) v
        else removeBracket(
            it.fold(v) { acc, cur ->
                val target = cur.value
                val ret = calcWithBracket(target)
                acc.replace(target, "$ret")
            }
        )
    }
}

fun calc(v: String): Double = removeBracket("(${trim(v)})").toDouble()

fun main(args: Array<String>) {
    val exps: Array<String> = arrayOf(
        "16 / 2 / 2 / 2",
        "-2 -3 + 0.4",
        "-2 * (-3 + 0.4) / -0.2",
        "-2 * (-3 + 0.4) / -0.2 + .55",
        "-2 - (-3 + -8 * (7 + 3)) + (0.4 / -0.2)",
    )
    for (exp in exps) {
        println("$exp = ${calc(exp)}")
    }
}

@hannut91 감사합니다.