백준 - 6198번 옥상 정원 꾸미기 (골드 5)

시간초과......

다른 방법은 떠오르지 않는다...

import java.io.*;
import java.util.*;

class Main{
    public static void main(String[] args) throws IOException{
        BufferedReader br=new BufferedReader(
                new InputStreamReader(System.in));
        BufferedWriter bw=new BufferedWriter(
                new OutputStreamWriter(System.out));

        int N=Integer.parseInt(br.readLine());
        int[] heights=new int[N];
        Stack <Integer> stack1=new Stack<>();
        Stack <Integer> stack2=new Stack<>();
        
        for(int i=0;i<N;i++){
            heights[i]=Integer.parseInt(br.readLine());
        }
        
        for(int i=N-1;i>=0;i--){
            stack1.push(heights[i]);
        }

        
        int height=0;
        int sum=0;
        while(!stack1.isEmpty()){
            height=stack1.pop();
            
            while(!stack1.isEmpty()&& height>stack1.peek()){
                stack2.push(stack1.pop());   
            }
            sum+=stack2.size();
            
            while(!stack2.isEmpty()){
                stack1.push(stack2.pop());
            }
        }

        bw.write(Integer.toString(sum));
        bw.flush();
        bw.close();
    }
}