273. Integer to English Words
Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1.
Example 1:
Input: 123 Output: "One Hundred Twenty Three"
Example 2:
Input: 12345 Output: "Twelve Thousand Three Hundred Forty Five"
思路：
把数字按照英文输出，这和有一题读阿拉伯数字是类似的，就是一个实现题，思想就是把
"Thousand", "Million", "Billion"作为单位，分段计算每一段应该读做多少，然后加上这个单位就可以。
代码：
java：
代码语言：javascript复制class Solution {
private static final String[] LESS_THAN_20 = {"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
private static final String[] TENS = {"", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
private static final String[] THOUSANDS = {"", "Thousand", "Million", "Billion"};
public String numberToWords(int num) {
if (num == 0) return "Zero";
String res = "";
int i = 0;
while(num > 0) {
if (num % 1000 != 0) res = helper(num % 1000) THOUSANDS[i] " " res;
num /= 1000;
i ;
}
return res.trim();
}
private String helper(int num) {
if (num == 0) {
return "";
} else if (num < 20) {
return LESS_THAN_20[num] " ";
} else if (num < 100) {
return TENS[num / 10] " " helper(num % 10);
} else {
return LESS_THAN_20[num / 100] " Hundred " helper(num % 100);
}
}
}
