231118 110 옮기기

public String[] solution(String[] s) {
	String[] answer = new String[s.length];

	for (int i = 0; i < s.length; i++) {
		answer[i] = solve(s[i]);
	}

	return answer;
}

public String solve(String s) {
	int cnt110 = 0;
	Stack<Character> st = new Stack<>();

	for (int i = 0; i < s.length(); i++) {
		st.push(s.charAt(i));

		if (st.size() < 3)
			continue;

		cnt110 = processStack(st, cnt110);
	}

	StringBuilder sb = new StringBuilder();
	int position = st.size();
	boolean flag = false;

	position = makeString(st, sb, position, flag);

	for (int i = 0; i < cnt110; i++)
		sb.insert(position, "110");

	return sb.toString();
}

private int processStack(Stack<Character> st, int cnt110) {
	char first = st.pop();
	char second = st.pop();
	char third = st.pop();

	if (first == '0' && second == '1' && third == '1') {
		cnt110++;
	} else {
		st.push(third);
		st.push(second);
		st.push(first);
	}
	return cnt110;
}

private int makeString(Stack<Character> st, StringBuilder sb, int position, boolean flag) {
	while (!st.isEmpty()) {
		char pop = st.pop();
		if (!flag && pop == '1')
			position--;
		if (pop == '0')
			flag = true;
		sb.insert(0, pop);
	}
	return position;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/77886