Integer to English Words.cpp

class Solution {
public:
    string one[19]={"One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten","Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"};

string ten[8]={"Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"};
    
    string helper(int n) {
        if(n >=1000000000) return helper(n/1000000000)+" Billion"+helper(n%1000000000);
        if(n>=1000000) return helper(n/1000000)+" Million"+helper(n%1000000);
    
        if(n>=1000) return helper(n/1000)+" Thousand"+helper(n%1000);
    
        if(n>=100) return helper(n/100)+" Hundred"+helper(n%100);
        
        if(n>=20) return " "+ten[n/10-2]+helper(n%10);
    
        if(n>=1) return " "+one[n-1];
        
        return "";
    }
    
    string numberToWords(int num) {
        string res="";
        
        if(num == 0)
            return "Zero";
        
        return helper(num).substr(1);
        
    }
};