백준 2493번 탑 [ Java ]

2493번: 탑

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

public class Main {

    public static void main(String[] args) throws IOException {
        // height, index
        Stack<int[]> tower = new Stack<>();
        StringBuilder sb = new StringBuilder();
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int N = Integer.parseInt(br.readLine());
        StringTokenizer st = new StringTokenizer(br.readLine());
        for (int i=1; i<=N; i++) {
            int now = Integer.parseInt(st.nextToken());
            while (!tower.isEmpty() && tower.peek()[0] < now)
                tower.pop();
            sb.append(tower.isEmpty() ? 0+" " : tower.get(tower.size()-1)[1]+" ");
            tower.push(new int[]{now, i});
        }
        System.out.print(sb);
    }
}