릿코드 1291. Sequential Digits 코틀린

low와 high사이에 있는 123,234같은 연속된수들을 모두 배열에담아 리턴
일단 123을 만들수있는 1~9까지 루프(i),
갯수를 맞추기위한 low의 length와 highLength사이의 루프(j)
0부터 j까지의 루프(k)
3가지가 필요함
어짜피  high가 10^9로 한정되어졌기때문에,유한범위내에서 돌아가서 for많이돌려도 됨
1~9루프야 상수급이고 j루프와 k루프로 O(n^2)정도인데 크기도 10정도라 10^2니까


정답

class Solution {
    fun sequentialDigits(low: Int, high: Int): List<Int> {
        val lowLength = low.toString().length
        val highLength = high.toString().length
        val resList= mutableListOf<Int>()



        for (i in 1..9){
            for (j in lowLength .. highLength){
                var tempString = ""
                for (k in 0 until j) {
                    if (k+i>9){
                        tempString=""
                        break
                    }
                    tempString=tempString.plus(k+i)
                }

                if (tempString!=""){
                    val tempInt = tempString.toInt()
                    if (tempInt>=low &&tempInt<=high) {
                        //println(tempString)
                        resList.add(tempString.toInt())
                    }
                }
            }


        }

        return resList.sorted()
    }
}