[알고리즘문제풀기] k의 개수

문제

내가 작성한 정답

class Solution {
    public int solution(int i, int j, int k) {
        int answer = 0;
        for(int a=i; a<=j; a++){
            for(String b: (a+"").split("")){
                String kk = k+"";
                if(b.equals(kk)) answer++;
            }
        }
        return answer;
   
 class Solution {
    public int solution(int i, int j, int k) {
        int answer = 0;
        for(int a=i; a<=j; a++){
            String aa = a+"";
            for(int b=0; b<aa.length(); b++){
                if(aa.charAt(b)==(char)(k+'0')) answer++;
            }
        }
        return answer;
    }
}

다른 사람들의 정답

class Solution {
    public int solution(int i, int j, int k) {
        String str = "";
        for(int a = i; a <= j; a++) {
            str += a+"";
        }

        return str.length() - str.replace(k+"", "").length();
    }
}


class Solution {
    public int solution(int i, int j, int k) {
        int answer = 0;

        for (int num = i; num <= j; num++){
            int tmp = num;
            while (tmp != 0){
                if (tmp % 10 == k)
                    answer++;
                tmp /= 10;
            }
        }
        return answer;
    }
}