240105 4단 고음

public int solution(int n) {
	return dfs(n, 0);
}

private int dfs(int value, int cnt) {
	if (value < 1 || 2 * Math.log(value) / Math.log(3) < cnt) {
		return 0;
	}
	if (value == 3) {
		return (cnt == 2) ? 1 : 0;
	}

	int result = 0;
	if (value % 3 == 0 && cnt >= 2) {
		result += dfs(value / 3, cnt - 2);
	}
	result += dfs(value - 1, cnt + 1);
	return result;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/1831