整数转换英文表示Java

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# 题目

将非负整数 num 转换为其对应的英文表示。

示例 1：

输入：num = 123
输出："One Hundred Twenty Three"

示例 2：

输入：num = 12345
输出："Twelve Thousand Three Hundred Forty Five"

示例 3：

输入：num = 1234567
输出："One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"

提示：

0 <= num <= 2<sup>31</sup> - 1

# 思路

先初始化英文数组，然后对给定数字取模、除以等去解析，注意从哪个数组取

# 解法


class Solution {
    String[] low = {"","One","Two","Three","Four","Five","Six","Seven","Eight","Nine"};
    String[] mid = {"Ten","Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"};
    String[] high = {"","","Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"};

    public String numberToWords(int num) {
        if(num==0){
            return "Zero";
        }
        int part1 = num%1000;
        num = num/1000;
        int part2 = num%1000;
        num = num/1000;
        int part3 = num%1000;
        num = num/1000;
        int part4 = num;
        String ans = "";
        if(part4!=0){
            ans = buildNumber(part4) + "Billion ";
        }
        if(part3!=0){
            ans = ans + buildNumber(part3) + "Million ";
        }
        if(part2!=0){
            ans = ans + buildNumber(part2) + "Thousand ";
        }
        if(part1!=0){
            ans = ans + buildNumber(part1);
        }
        return ans.trim();
    }

    public String buildNumber(int num){
        int a = num%10;
        num = num/10;
        int b = num%10;
        num = num/10;
        int c = num;
        String ans = "";
        if(c!=0){
            ans = low[c] + " " + "Hundred ";
        }
        if(b==1){
            ans = ans + mid[a];
        }else if(b==0){
            ans = ans + low[a];
        }else {
            ans = ans + high[b] + " " + low[a];
        }
        return ans.trim() + " ";
    }
    
}

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# 总结

分析出几种情况，然后分别对各个情况实现