백준 소스코드 [C++] 1918 후위 표기식

https://www.acmicpc.net/problem/1918

1918번: 후위 표기식

백준 소스코드 [C++] 1918 후위 표기식

#include <iostream>
#include <stack>
#include <string>
int change(char x) {
	if (x == '+' || x == '-') return 1;
	if (x == '*' || x == '/') return 2;
	if (x == '(') return 0;
}
using namespace std;
int main() {
	string xx;
	getline(cin, xx);
	stack<char> ss;
	for (int i = 0;i < (int)xx.length();i++) {
		if ('A' <= xx[i] && xx[i] <= 'Z') cout << xx[i];
		else if (xx[i] <= '(') ss.push(xx[i]);
		else if (xx[i] <= ')') {
			while (ss.top() != '(') {
				cout << ss.top();
				ss.pop();
			}
			ss.pop();
		}
		else {
			while (!ss.empty() && (change(ss.top()) >= change(xx[i]))) {
				cout << ss.top();
				ss.pop();
			}
			ss.push(xx[i]);
		}
	}
	while (!ss.empty()) {
		cout << ss.top();
		ss.pop();
	}

	return 0;
}