[Leetcode] 273. Integer to English Words-优快云博客

本文链接：https://blog.youkuaiyun.com/Renoler/article/details/102265032

本文详细介绍了一种将整数转换为英文单词的算法实现，通过将数字分割为billion, million, thousand等部分，分别处理每一位数字，最终组合成完整的英文单词表示。算法包括处理个位数、两位数、三位数的函数，并提供了完整的代码示例。

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

Solution:
重点在于如何把长数分割成小的部分考虑（分别为billion，million，thousand，各部分均有三位数字）

class Solution {
    public String single(int num) {
        switch(num) {
            case 1: return "One";
            case 2: return "Two";
            case 3: return "Three";
            case 4: return "Four";
            case 5: return "Five";
            case 6: return "Six";
            case 7: return "Seven";
            case 8: return "Eight";
            case 9: return "Nine";
        }
        return "";
    }
        
    public String twoDigits(int num) {
    switch(num) {
        case 10: return "Ten";
        case 11: return "Eleven";
        case 12: return "Twelve";
        case 13: return "Thirteen";
        case 14: return "Fourteen";
        case 15: return "Fifteen";            
        case 16: return "Sixteen";
        case 17: return "Seventeen";
        case 18: return "Eighteen";
        case 19: return "Nineteen";
        }
        return "";
    }
    
    public String decimal(int num) {
    switch(num) {
        case 2: return "Twenty";
        case 3: return "Thirty";
        case 4: return "Forty";
        case 5: return "Fifty";
        case 6: return "Sixty";
        case 7: return "Seventy";            
        case 8: return "Eighty";
        case 9: return "Ninety";
        }
        return "";
    }
    
    public String twoString(int num) {
        if (num < 10) {
            return single(num);
        } else if (num < 20) {
            return twoDigits(num);
        } else {
            int tenner = num/10;
            int res = num%10;
            if (res == 0) {
                return decimal(tenner);
            } else {
                return decimal(tenner) + " " + single(res);
            }
        }
        
    }
    
    public String three(int num) {
        int hundred = num/100;
        int res = num%100;
        if (hundred == 0) {
            return twoString(num);
        } else {
            if (res == 0) {
                return single(hundred) + " Hundred";
            } else {
                return single(hundred) + " Hundred " + twoString(res);
            }
        }
    }
    
    public String numberToWords(int num) {
        if (num == 0) {
            return "Zero";
        }
        
        int billion = num/1000000000;
        int million = (num-billion*1000000000)/1000000;
        int thousand = (num-billion*1000000000-million*1000000)/1000;
        int res = num-billion*1000000000-million*1000000-thousand*1000;
        
        String s = "";
        if (billion != 0) {
            s += three(billion) + " Billion";
        }
        if (million != 0) {
            if(!s.isEmpty()) {
                s += " ";
            }
            s += three(million) + " Million";
        }
        if (thousand != 0) {
            if(!s.isEmpty()) {
                s += " ";
            }
            s += three(thousand) + " Thousand";
        }
        if (res != 0) {
            if(!s.isEmpty()) {
                s += " ";
            }
            s += three(res);
        }
        return s;    
    }
}