273. Integer to English Words

public class Solution {
    private string[] belowTwenty = {"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
    private string[] tens = {"", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
    private string[] thousands = {"", "Thousand", "Million", "Billion"};
    public string NumberToWords(int num) {
        if (num == 0) return "Zero";
        int i = 0;
        string result = "";
        
        while (num > 0) {
            if (num % 1000 != 0) {
                result = Helper(num % 1000) + thousands[i] + " " + result;
            }
            num /= 1000;
            i++;
        }
        return result.Trim();
    }
    private string Helper(int num) {
        if (num == 0) return "";
        else if (num < 20) return belowTwenty[num] + " ";
        else if (num < 100) return tens[num / 10] + " " + Helper(num % 10);
        else return belowTwenty[num / 100] + " Hundred " + Helper(num % 100);
    }
}

#include <bits/stdc++.h>
using namespace std;

// Auto-generated C++ draft from the C# solution. Review containers, LINQ and helper types before submit.
class Solution {
public:
    private vector<string> belowTwenty = {"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
    private vector<string> tens = {"", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
    private vector<string> thousands = {"", "Thousand", "Million", "Billion"};
    public string NumberToWords(int num) {
        if (num == 0) return "Zero";
        int i = 0;
        string result = "";
        
        while (num > 0) {
            if (num % 1000 != 0) {
                result = Helper(num % 1000) + thousands[i] + " " + result;
            }
            num /= 1000;
            i++;
        }
        return result.Trim();
    }
    private string Helper(int num) {
        if (num == 0) return "";
        else if (num < 20) return belowTwenty[num] + " ";
        else if (num < 100) return tens[num / 10] + " " + Helper(num % 10);
        else return belowTwenty[num / 100] + " Hundred " + Helper(num % 100);
    }
}

class Solution {
    private final String[] belowTwenty = {"", "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";
        int i = 0;
        String result = "";
        
        while (num > 0) {
            if (num % 1000 != 0) {
                result = helper(num % 1000) + thousands[i] + " " + result;
            }
            num /= 1000;
            i++;
        }
        return result.trim();
    }

    private String helper(int num) {
        if (num == 0) return "";
        else if (num < 20) return belowTwenty[num] + " ";
        else if (num < 100) return tens[num / 10] + " " + helper(num % 10);
        else return belowTwenty[num / 100] + " Hundred " + helper(num % 100);
    }
}

var numberToWords = function(num) {
    if (num === 0) return "Zero";

    const belowTwenty = ["", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"];
    const tens = ["", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"];
    const thousands = ["", "Thousand", "Million", "Billion"];
    
    let result = "";
    let i = 0;
    
    while (num > 0) {
        if (num % 1000 !== 0) {
            result = helper(num % 1000) + thousands[i] + " " + result;
        }
        num = Math.floor(num / 1000);
        i++;
    }
    return result.trim();
};

function helper(num) {
    const belowTwenty = ["", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"];
    const tens = ["", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"];
    
    if (num === 0) return "";
    else if (num < 20) return belowTwenty[num] + " ";
    else if (num < 100) return tens[Math.floor(num / 10)] + " " + helper(num % 10);
    else return belowTwenty[Math.floor(num / 100)] + " Hundred " + helper(num % 100);
}

class Solution:
    def numberToWords(self, num: int) -> str:
        if num == 0:
            return "Zero"
        
        def helper(n):
            if n == 0:
                return ""
            elif n < 20:
                return below_twenty[n] + " "
            elif n < 100:
                return tens[n // 10] + " " + helper(n % 10)
            else:
                return below_twenty[n // 100] + " Hundred " + helper(n % 100)
        
        below_twenty = ["", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"]
        tens = ["", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"]
        thousands = ["", "Thousand", "Million", "Billion"]
        
        result = ""
        i = 0
        
        while num > 0:
            if num % 1000 != 0:
                result = helper(num % 1000) + thousands[i] + " " + result
            num //= 1000
            i += 1
        
        return result.strip()

package main

import (
    "strings"
    "strconv"
)

func numberToWords(num int) string {
    if num == 0 {
        return "Zero"
    }

    belowTwenty := []string{"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"}
    tens := []string{"", "Ten", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"}
    thousands := []string{"", "Thousand", "Million", "Billion"}

    var result string
    i := 0

    for num > 0 {
        if num%1000 != 0 {
            result = helper(num%1000, belowTwenty, tens) + thousands[i] + " " + result
        }
        num /= 1000
        i++
    }
    return strings.TrimSpace(result)
}

func helper(num int, belowTwenty, tens []string) string {
    if num == 0 {
        return ""
    } else if num < 20 {
        return belowTwenty[num] + " "
    } else if num < 100 {
        return tens[num/10] + " " + helper(num%10, belowTwenty, tens)
    } else {
        return belowTwenty[num/100] + " Hundred " + helper(num%100, belowTwenty, tens)
    }
}

Explanation

Algorithm

1️⃣

Обработка чисел до 20 и кратных 10 до 90:

Создать массивы или словари для чисел от 1 до 19 и для кратных 10 от 20 до 90.

Если число попадает в эти диапазоны, сразу вернуть соответствующее словесное представление.

2️⃣

Обработка сотен, тысяч, миллионов и миллиардов:

Разделить число на группы по три цифры (единицы, тысячи, миллионы, миллиарды).

Для каждой группы сформировать словесное представление с использованием рекурсивной функции для чисел от 1 до 999.

3️⃣

Формирование окончательного результата:

Собрать словесное представление всех групп, добавив соответствующие суффиксы (тысячи, миллионы, миллиарды).

Соединить все части в одну строку, удалив лишние пробелы.

😎