Integer to English Words_integertoenglishwords-优快云博客

本文介绍了一种将非负整数转换为其英文单词表示的方法，确保输入值小于2^31-1。通过详细的Java代码示例展示了如何处理不同数量级的数字（如千、百万等），并解决了实现过程中可能遇到的细节问题。

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题目描述：

Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 2³¹ - 1.

For example,

123 -> "One Hundred Twenty Three"
12345 -> "Twelve Thousand Three Hundred Forty Five"
1234567 -> "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"

这个题难度没啥难度，就是考细节，各种空格问题。

public class Solution {
    public String numberToWords(int num) {
		if(num==0)
			return "Zero";
        StringBuilder sb=new StringBuilder();
        String str=String.valueOf(num);
        int n=0;
        while(num>0){
        	n++;
        	num/=10;
        }
        int[] a=new int[(n-1)/3+1];
        int firstLen=(n-1)%3+1;
        a[0]=Integer.parseInt(str.substring(0, firstLen));
        for(int i=1;i<a.length;i++){
        	a[i]=Integer.parseInt(str.substring(firstLen, firstLen+3));
        	firstLen+=3;
        }
        for(int i=0;i<a.length;i++){
        	sb.insert(0, getNumberStr(a[a.length-1-i],i,a.length));
        }
        return sb.toString();
    }
	public String getNumberStr(int num, int k ,int len) {
		String[] strs1=new String[]{"One","Two","Three","Four","Five","Six","Seven","Eight","Nine"};
		String[] strs2=new String[]{"Ten","Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"};
		String[] strs3=new String[]{"Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"};
		StringBuilder sb=new StringBuilder();
		//当num==0时直接返回""
		if(num==0)
			return sb.toString();
	      //第一个三位数分组前面没有空格，后面的三位数分组前面有空格
		if(k<len-1)
			sb.append(" ");
		int hundred =num/100;
		if(hundred>0) {
			sb.append(strs1[hundred-1]).append(" Hundred");
			if(num%100!=0)
				sb.append(" ");
		}
		int ten =num/10%10;
		//十位数分三种情况讨论
		if(ten==0){
			int one=num%10;
			if(one>0)
				sb.append(strs1[num%10-1]);
		}
		if(ten==1){
			sb.append(strs2[num%10]);
		}
		if(ten>1){
			sb.append(strs3[ten-2]);
			int one=num%10;
			if(one!=0)
				sb.append(" "+strs1[num%10-1]);
		}
		switch (k) {
		case 1:
			sb.append(" Thousand");
			break;
		case 2:
			sb.append(" Million");
			break;
		case 3:
			sb.append(" Billion");
			break;
		default:
			break;
		}
		return sb.toString();
	}
}