[백준] 스택 수열

import java.util.ArrayList; import java.util.List; import java.util.Scanner; import java.util.Stack; public class B1874 { /* Stack follows LIFO order. * You may push numbers 1 to n and pop such that * sequence is built. If every time a value is pushed * numbers are in ascending order, (the value on top is the maximum number) * define a method that judges whether a given sequence may be created using * stack data structure and if possible in what order push and pops are processed. */ public void createSequence(int seqLength, int[] sequence) { Stack<Integer> pushAndPop = new Stack<>(); List<String> savedOperators = new ArrayList<>(); int cnt = 0; for (int i = 1; i <= seqLength; i++) { pushAndPop.push(i); savedOperators.add("+"); while (cnt < seqLength && !pushAndPop.empty() && sequence[cnt] == pushAndPop.peek()) { pushAndPop.pop(); savedOperators.add("-"); cnt++; } } if (!pushAndPop.empty()) System.out.println("NO"); else for (String savedOperator : savedOperators) { System.out.println(savedOperator); } } public static void main(String[] args) { Scanner sc = new Scanner(System.in); int size = sc.nextInt(); int[] sequence = new int[size]; for (int i = 0; i < size; i++) { sequence[i] = sc.nextInt(); } B1874 b1874 = new B1874(); b1874.createSequence(size, sequence); } }