첫 풀이 [비효율적]

class Solution {
    public String solution(int n, int t, int m, int p) {
        String answer = "";

        int mySaveNumCount = 0;

        int number = 0;
        String numberString = "0";
        int numCount = 0;

        int turnCount = 1;

        while(mySaveNumCount != t){
            if(numCount == numberString.length()){
                number++;

                numberString = Integer.toString(number, n);

                numCount = 0;
            }

            if(turnCount == p){
                answer += numberString.charAt(numCount);
                mySaveNumCount++;
            }

            if(turnCount < m){
                turnCount++;
            }else{
                turnCount = 1;
            }

            numCount++;
        }

        return answer.toUpperCase();
    }
}

두번째 풀이 [시간 단축]

class Solution {
    public String solution(int n, int t, int m, int p) {
        StringBuilder answer = new StringBuilder();

        int number = 0;
        StringBuilder allNumberString = new StringBuilder();

        //우리가 필요한 길이만큼 String을 합친다.
        while (allNumberString.length() < t * m){
            allNumberString.append(Integer.toString(number, n));
            number++;
        }

        //내 차례에 맞는 char을 더하면서 answer를 만든다.
        for (int round = 0; round < t; round++) {
            answer.append(allNumberString.charAt(p - 1 + (round * m)));
        }

        return answer.toString().toUpperCase();
    }
}