LeetCode 0273 - Integer to English Words

Integer to English Words

Desicription

Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 2^31 - 1.

Example 1:

代码语言：javascript复制

Input: 123
Output: "One Hundred Twenty Three"

Example 2:

代码语言：javascript复制

Input: 12345
Output: "Twelve Thousand Three Hundred Forty Five"

Example 3:

代码语言：javascript复制

Input: 1234567
Output: "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"

Example 4:

代码语言：javascript复制

Input: 1234567891
Output: "One Billion Two Hundred Thirty Four Million Five Hundred Sixty Seven Thousand Eight Hundred Ninety One"

Solution

代码语言：javascript复制

class Solution {
private:
    const vector<string> one_to_nineteen = {
            "",
            "One",
            "Two",
            "Three",
            "Four",
            "Five",
            "Six",
            "Seven",
            "Eight",
            "Nine",
            "Ten",
            "Eleven",
            "Twelve",
            "Thirteen",
            "Fourteen",
            "Fifteen",
            "Sixteen",
            "Seventeen",
            "Eighteen",
            "Nineteen"
    };

    const vector<string> twenty_to_ninety = {
            "",
            "",
            "Twenty",
            "Thirty",
            "Forty",
            "Fifty",
            "Sixty",
            "Seventy",
            "Eighty",
            "Ninety"
    };

    string get_words(int num) {
        if(num >= (int)1e9) {
            return get_words(num / (int)1e9)   " Billion"   get_words(num % (int)1e9);
        } else if(num >= (int)1e6) {
            return get_words(num / (int)1e6)   " Million"   get_words(num % (int)1e6);
        } else if(num >= (int)1e3) {
            return get_words(num / (int)1e3)   " Thousand"   get_words(num % (int)1e3);
        } else if(num >= (int)1e2) {
            return get_words(num / (int)1e2)   " Hundred"   get_words(num % (int)1e2);
        } else if(num >= 20) {
            return string(" ")   twenty_to_ninety[num / 10]   get_words(num % 10);
        } else if(num >= 1) {
            return string(" ")   one_to_nineteen[num];
        } else {
            return string("");
        }
    }

public:
    string numberToWords(int num) {
        if(num == 0) {
            return "Zero";
        } else {
            return get_words(num).substr(1);
        }
    }
};

input integer

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