leetcode 面试题 16.08.整数的英语表示

原题如下

https://leetcode-cn.com/problems/english-int-lcci/

题解

/*
 *@v7fgg
 *执行用时 :17 ms, 在所有 Java 提交中击败了27.86%的用户
 *内存消耗 :39.8 MB, 在所有 Java 提交中击败了100.00%的户
 *2020年6月18日 22:24
 */
class Solution {
    public String numberToWords(int num) {
        //考虑特殊情况的0
        if(num==0){return "Zero";}
        String ans="";
        //原数字在后面还要用到，因此复制一份，这里只需要考虑绝对值
        int m=Math.abs(num);
        int yi=m%1000;//1000以内的值，也就是后三位
        int qian=m/1000%1000;//多少千thousand
        int baiwan=m/1000000%1000;//多少百万million
        int shiyi=m/1000000000;//多少十亿billion
        if(yi>0){
            ans=in1000(yi);
        }
        if(qian>0){
            ans=in1000(qian)+" Thousand "+ans;
        }
        if(baiwan>0){
            ans=in1000(baiwan)+" Million "+ans;
        }
        if(shiyi>0){
            ans=in1000(shiyi)+" Billion "+ans;
        }
        //考虑负数的情况
        if(num<0){ans="Negative "+ans;}
        return ans.trim();
    }
    public String in1000(int a){
        //此函数是把一个1000以内的数字变成字符串
        String shuzi1[]=new String[]{"","One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten","Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"};
        String shuzi2[]=new String[]{"","Ten","Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"};
        String r="";
        if(a%100<20){
            r=shuzi1[a%100];
            a/=100;
        }
        else{
            r=shuzi1[a%10];
            a/=10;
            if(a>0){
                //要去掉空格，因为会出现比如：3000000 thirty thousand
                r=(shuzi2[a%10]+" "+r).trim();
                a/=10;
            }
        }
        if(a>0){
            //去空格是因为会出现比如：100000 one hundred thousand
            r=(shuzi1[a]+" Hundred "+r).trim();
        }
        return r;
    }
}