[백준] 1874: 스택 수열

1874번: 스택 수열

#include <iostream>
#include <string>
#include <stack>

using namespace std;
int main() {
	ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
	stack<int> stk;
	string hist;
	int n; cin >> n;
	int m = 0;
	while (n--) {
		int input; cin >> input;
		if (m < input) {
			while (m < input) {
				stk.push(++m);
				hist += '+';
			}
			stk.pop();
			hist += '-';
		}
		else {
			if (!stk.empty()) {
				if (stk.top() == input) {
					stk.pop();
					hist += '-';
				}
				else if (stk.top() > input) {
					cout << "NO" << endl;
					return 0;
				}
			}
		}
	}

	for (char& ans : hist) { cout << ans << '\n'; }
}