LeetCode: 273. Integer to English Words

Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than ​​23^1 - 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"

解题思路

根据英文读法模拟求解

AC 代码

class Solution {
private:
    // 1000 以内
    string numberToWordsRef(int num)
    {
        unordered_map<int,string> numbers
                 = {{0,"Zero"},{1,"One"},{2,"Two"},{3,"Three"},{4,"Four"},{5,"Five"},{6,"Six"},
                     {7,"Seven"},{8,"Eight"},{9,"Nine"},{10,"Ten"},{11,"Eleven"},{12,"Twelve"},
                     {13,"Thirteen"},{14,"Fourteen"},{15,"Fifteen"},{16,"Sixteen"},{17,"Seventeen"},
                     {18,"Eighteen"},{19,"Nineteen"},{20,"Twenty"},{30,"Thirty"},{40,"Forty"},
                     {50,"Fifty"},{60,"Sixty"},{70,"Seventy"},{80,"Eighty"},{90,"Ninety"}};
        string ans;
        if(num / 100 > 0)
        {
            ans = numbers[num/100] + " Hundred";
        }
        if(num % 100 > 20)
        {
            if(ans.empty() == false) ans += " ";

            ans += (numbers[(num%100)/10*10]);
            if(num % 10 != 0)
            {
                ans += (" " + numbers[(num%10)]);
            }
        }
        else if(num % 100 != 0)
        {
            if(ans.empty() == false) ans += " ";
            ans += numbers[(num%100)];
        }
        
        return ans;
    }
public:
    string numberToWords(int num) {
        string magnitudes[] = {"Thousand", "Million", "Billion", "Trillion", "Trilliard"};
        string ans;
         
        if(num == 0) return "Zero";
        
        int cnt = 0;
        while(num != 0)
        {
            int temp = num % 1000;
            num /= 1000;
            
            if(cnt == 0) 
            {
                ans = numberToWordsRef(temp);
            }
            else 
            {
                if(temp != 0)
                {
                    if(ans.empty() == false)
                    {
                        ans = " " + ans;
                    }
                    ans = numberToWordsRef(temp) + " " + magnitudes[cnt-1] + ans;
                }
            }
            
            ++cnt;
        }
        return ans;
    }
};