def numberToWords(self, num):
to19 = 'One Two Three Four Five Six Seven Eight Nine Ten Eleven Twelve ' \
'Thirteen Fourteen Fifteen Sixteen Seventeen Eighteen Nineteen'.split()
tens = 'Twenty Thirty Forty Fifty Sixty Seventy Eighty Ninety'.split()
def words(n):
if n < 20:
return to19[n1:n]
if n < 100:
return [tens[n/102]] + words(n%10)
if n < 1000:
return [to19[n/1001]] + ['Hundred'] + words(n%100)
for p, w in enumerate(('Thousand', 'Million', 'Billion'), 1):
if n < 1000**(p+1):
return words(n/1000**p) + [w] + words(n%1000**p)
return ' '.join(words(num)) or 'Zero'
Recursive Python


With a little bit of math you don't need to loop but maybe the loop is easier to read?
https://discuss.leetcode.com/topic/68311/shortcleanjavasolutionusingmathlog10andmathpow

Very brilliant solution to use recursion, so the code is clean.
This is just a rewrite in C++, which also shows how convenient Python is in term of string manipulation :)
typedef vector<string> VS; VS to19 = { "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"}; VS tens = { "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety" }; VS units = {"Thousand", "Million", "Billion"}; VS join(const VS& w1, const VS& w2) { VS w(w1); w.insert(w.end(), w2.begin(), w2.end()); return w; } string numberToWords(int n) { VS ws(words(n)); if (ws.empty()) return "Zero"; string res; for (auto& w : ws) res += (w + " "); return res.substr(0, res.size()1); } VS words(int n) { if (n == 0) return { }; if (n < 20) return { to19[n1] }; if (n < 100) return join({ tens[n/102] }, words(n%10)); if (n < 1000) return join(join({ to19[n/1001] }, { "Hundred" }), words(n%100)); int base = 1000; for (auto unit : units) { if (unit == "Billion" or n < 1000*base) return join(join(words(n/base), {unit}), words(n%base)); base *= 1000; } }