[刷题防痴呆] 0273 - 整数转换英文表示 (Integer

题目地址

https://leetcode.com/problems/integer-to-english-words/description/

题目描述

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"
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"

思路

切割拼接.

关键点

• 这题切割为, 10以内, 20以内, 100以内, 1000以内, 1百万以内, 10亿(billion)以内, 和10亿以上.
• 不停切割相加, 最后result trim.
• 注意, 0, 单独return.
• 注意, 100以下拼接时候, 记得加" ".

代码

• 语言支持：Java

class Solution {
    public String numberToWords(int num) {
        if (num == 0) {
            return "Zero";
        }
        
        return helper(num);
    }
    
    private String helper(int num) {
        String[] belowTen = {"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine"};
        String[] belowTwenty = {"Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
        String[] belowHundred = {"", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
        
        String result;
        
        if (num < 10) {
            result = belowTen[num];
        } else if (num < 20) {
            result = belowTwenty[num - 10];
        } else if (num < 100) {
            result = belowHundred[num / 10] + " " + helper(num % 10);
        } else if (num < 1000) {
            result = helper(num / 100) + " Hundred " + helper(num % 100);
        } else if (num < 1000000) {
            result = helper(num / 1000) + " Thousand " + helper(num % 1000);
        } else if (num < 1000000000) {
            result = helper(num / 1000000) + " Million " + helper(num % 1000000);
        } else {
            result = helper(num / 1000000000) + " Billion " + helper(num % 1000000000); 
        }
        
        return result.trim();
    }
}