내 풀이

class Solution {
    public int solution(int i, int j, int k) {
        int answer = 0;
        String str = "";
        for(int a = i ; a <=j ; a++){
            str += Integer.toString(a);
        }
        for(int a = 0 ; a<str.length() ; a++){
            if((Integer.toString(k)).equals(str.substring(a,a+1))){  
                ++answer;
            }
        }
        return answer;
    }
}