프로그래머스 - 주식가격 (스택/큐)

    public int[] solution(int[] prices) {
 
        int[] answer = new int[prices.length];
 
        Stack<Integer> priceSt = new Stack<>();
        Stack<Integer> indexSt = new Stack<>();
 
        priceSt.push(prices[0]);
        indexSt.push(0);
 
        for (int i = 1; i < prices.length; i++) {
            while (true) {
                if (!priceSt.isEmpty() && priceSt.peek() > prices[i]) {
                    int idx = indexSt.pop();
                    priceSt.pop();
                    answer[idx] = i - idx;
                } else
                    break;
 
            }
 
            priceSt.push(prices[i]);
            indexSt.push(i);
 
        }
 
        while (!priceSt.isEmpty()) {
            int idx = indexSt.pop();
            priceSt.pop();
            answer[idx] = (prices.length - 1) - idx;
        }
 
        // for(int i : answer){
        //     System.out.println(i);
        // }
 
        return answer;
    }