import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayDeque; import java.util.Iterator; import java.util.LinkedList; import java.util.ListIterator; public class Main { public static void main(String[] args) throws IOException { new Main().solution(); } void solution() throws IOException { // 0. input 받기 long answer = 0; BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); int N = Integer.parseInt(br.readLine()); LinkedList stack = new LinkedList<>(); // stack int height = Integer.parseInt(br.readLine()); stack.add(height); for (int i = 1; i < N; i++) { height = Integer.parseInt(br.readLine()); while (!stack.isEmpty() && height > stack.getLast()) { stack.removeLast(); answer ++; } if (!stack.isEmpty()) { if (height == stack.getLast()) { for (Integer integer : Reversed.reversed(stack)) { answer++; if (integer != height) break; } } else { // height < stack.getLast() answer++; } } stack.add(height); } System.out.println(answer); } public static class Reversed implements Iterable { private final LinkedList original; public Reversed(LinkedList original) { this.original = original; } public Iterator iterator() { final ListIterator i = original.listIterator(original.size()); return new Iterator() { public boolean hasNext() { return i.hasPrevious(); } public T next() { return i.previous(); } public void remove() { i.remove(); } }; } public static Reversed reversed(LinkedList original) { return new Reversed(original); } } }

[BOJ 3015] 오아시스 재결합: Java