题解 | #阿拉伯数字转中文#

import java.util.*;


public class Solution {
    public static void main(String[] args) {
        String s = new Solution().num2cn(1000000007);
        System.out.println(s);
        System.out.println(new Solution().trans4(new char[]{'0','0','0','7'}));
    }
    StringBuilder res;
    String[] bigUnit={"","万","亿"};
    String[] shu={
            "零",
            "一",
            "二",
            "三",
            "四",
            "五",
            "六",
            "七",
            "八",
            "九"
    };
    String[] unit={"","十","百","千"};
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param n int整型 
     * @return string字符串
     */
    public String num2cn (int n) {
        res=new StringBuilder();
        // one trick
        if(n==0){
            return "零";
        }
        
        if(n<0){
            res.append("负");
            n=-n;
        }
        
        List<String> duan4=new ArrayList<>();
        
        StringBuilder n2str = new StringBuilder(String.valueOf(n));
        int strLen = n2str.length();
        // one trick
        while(strLen >4){
            //  n==0需要单独考虑
            duan4.add(n2str.substring(strLen-4).toString());
            n2str.delete(strLen-4,strLen);
            strLen-=4;
        }
        if(strLen>0)
            duan4.add(n2str.toString());
        
        for(int i=duan4.size()-1;i>=0;i--){
            String cur=trans4(String.valueOf(duan4.get(i)).toCharArray());
            String bU=bigUnit[i];
            // one trick
            if("".equals(cur))
                bU="";
            res.append(cur).append(bU);
        }
        
        // one trick
        return res.toString().replaceAll("^一十","十");
    }
    public String trans4 (char[] duan){
        StringBuilder cur=new StringBuilder();
        for(int i=0;i<duan.length;i++){
            String curShu=shu[duan[i]-'0'];
            String u=unit[duan.length-i-1];
            // one trick
            if("零".equals(curShu)){
                u="";
            }
            cur.append(curShu).append(u);
        }
        return handleZero(cur.toString());
    }
    String handleZero(String s){
        //two trick
        s=s.replaceAll("零+","零");
        if(s.endsWith("零"))
            return s.substring(0,s.length()-1);
        return s;
    }
}