LeetCode 273.Integer to English Words【Java】

题目描述

Integer to English Words

AC代码

这个题的意思呢就是给你一个数字，让你把它所对应的英文读法表示出来。按照英文读一个数有一个特点就是每三个数是一组（可以观察一下给的样例读法）。也就是说我们可以这样表示一个数：其中下划线处的数组范围为1~999（最后一个下划线中，0这个数字单独拿出来特判），__million__billion__thousand___。处理每一个下划线部分可以单独写一个part函数，也就是说输入一个1000以内的数字，part方法可以返回其对应的英语读法，到最后每一部分各自拼接上对应的million/billion/thousand就可以了。

class Solution {
    String[] small={"Zero","One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten",
        "Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"};
    String[] decade={"","","Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"};
    String[] big={"Billion","Million","Thousand",""};
    public String numberToWords(int num) {
    	//特判0。
        if(num==0) return small[0];
        String res="";
        for(int i=1000000000,j=0;i>0;i/=1000,j++)
        {
            if(num>=i){
                res+=part(num/i)+big[j]+' ';
                num%=i;
            }
        }
        while(res.charAt(res.length()-1)==' ') res=res.substring(0,res.length()-1);
        return res;
    }

    String part(int num){
        String res="";
        if(num>=100){
            //此处需要注意Hundred前后都有空格
            res+=small[num/100]+" Hundred ";
            num%=100;
        }
        if(num==0) return res;
        //小于20的，可以直接加
        if(num>=20){
            res+=decade[num/10]+' ';
            num%=10;
        }
        if(num==0) return res;
        res+=small[num]+' ';
        return res;
    }
}