[백준][Java] 1935번 후위 표기식2 (스택)

double형 [n]자리까지 표기 -> String.format("%.[n]f, [double Value]);

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Stack;
 
 
 
public class Main {
        
    private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
    
    public static void main(String[] args) throws IOException{
        int N = stoi(br.readLine());
        char[] str = br.readLine().toCharArray();
        double[] num = new double[26];
        for(int i=0; i<N; i++)
            num[i] = Double.parseDouble(br.readLine());
        
        Stack<Double> st = new Stack<>();
        for (char c : str) {
            if('A'<=c && c<='Z') {
                st.push(num[c-'A']);
            }
            else {
                if(c=='+') {
                    st.push(st.pop()+st.pop());
                }
                else if (c == '-') {
                    double back = st.pop();
                    double front = st.pop();
                    st.push(front-back);
                } 
                else if (c == '*') {
                    st.push(st.pop()*st.pop());
                } 
                else if (c == '/') {
                    double back = st.pop();
                    double front = st.pop();
                    st.push(front/back);
                }
            }
        }
        System.out.println(String.format("%.2f", st.pop()));
        
        
        
//        bw.write("");
//        bw.flush();
//        bw.close();
    }
 
    private static int stoi(String input) {
        return Integer.parseInt(input);
    }
}