PAT 乙级真题——1002 写出这个数 (20 分)

题目来源：PAT 乙级真题——1002 写出这个数 (20 分)

import java.util.*;
public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        int sum = 0;
        for(int i = 0 ; i < s.length() ; i++) {
            int n = s.charAt(i) - '0';
            sum += n;
        }
        int yu = 0;
        String[] num = {"ling","yi","er","san","si","wu","liu","qi","ba","jiu"};
        Stack<String> st = new Stack<>();
        int i = 0;
        if(sum == 0) {  // 特殊情况
            System.out.println("ling");
            return;
        }
        while(sum > 0) {
            yu = sum % 10;
            st.push(num[yu]);
            sum /= 10;
        }
        while(!st.empty()) {
            System.out.print(st.pop());
            if(st.size() == 0) {    // 做去除空格的判断
                continue;
            } else {
                System.out.print(" ");
            }
        }
    }
}