LeetCode-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" Example 3: Input: 1234567 Output: "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven" Example 4: Input: 1234567891 Output: "One Billion Two Hundred Thirty Four Million Five Hundred Sixty Seven Thousand Eight Hundred Ninety One"
分成了三种状态。
0-19
20,30,40,...90
thousand, million, billion
所以,给一个三位数,如何转换成英语,这个是核心功能。
于是就用几个数组。
注意的地方是:
else if (num < 100) {
return TENS[num / 10] + " " + helper(num % 10);
}
必须得用 helper(num % 10)
为什么不能直接 LESS_THAN_20[num % 10] + " "
因为如果是0,不用加空格。你这里无法判断。于是交给helper
class Solution { private 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 final String[] TENS = {"", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"}; private final String[] THOUSANDS = {"", "Thousand", "Million", "Billion"}; public String numberToWords(int num) { if (num == 0) { return "Zero"; } String ret = ""; int i = 0; while (num > 0) { if (num % 1000 != 0) { ret = helper(num % 1000) + THOUSANDS[i] + " " + ret; } num = num / 1000; i++; } return ret.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); } } }
posted on 2018-07-02 07:11 IncredibleThings 阅读(96) 评论(0) 编辑 收藏 举报