[백준] 2493

 

스택을 활용하되 해당 타워의 인덱스를 저장할 자료구조를 활용해야한다.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Stack;
import java.util.StringTokenizer;

public class Main {
    static class Top {
        int idx;
        int height;
        
        Top(int idx, int height) {
            this.idx = idx;
            this.height = height;
        }
    }
    
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb = new StringBuilder();

        int N = Integer.parseInt(br.readLine());

        Stack<Top> stack = new Stack<>();

        StringTokenizer st = new StringTokenizer(br.readLine());

        for (int i = 1; i <= N; i++) {
            int num = Integer.parseInt(st.nextToken());

                while (!stack.isEmpty()) {
                    if (stack.peek().height < num) {
                        stack.pop();
                    }
                    else {
                         sb.append(stack.peek().idx + " ");
                         break;
                    }
                
                }
                if (stack.isEmpty()) {
                   sb.append("0 ");
                }
                stack.push(new Top(i,num));
            
        }
        System.out.println(sb);
    }
}