leetcode_c++：Integer to English Words(273)

Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1.

For example,

123 -> “One Hundred Twenty Three”

12345 -> “Twelve Thousand Three Hundred Forty Five”

1234567 -> “One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven”

http://blog.csdn.net/u012243115/article/details/48134075

class Solution {
public:
string helper(int num)
{
const static char* less_ten[] =
{ "", " One", " Two", " Three", " Four", " Five", " Six", " Seven", " Eight", " Nine" };

const static char* less_twenty[] =
{ " Ten", " Eleven", " Twelve", " Thirteen", " Fourteen", " Fifteen", " Sixteen", " Seventeen", " Eighteen", " Nineteen" };

const static char* less_hundred[] =
{ "", "", " Twenty", " Thirty", " Forty", " Fifty", " Sixty", " Seventy", " Eighty", " Ninety" };

string s;

if (num != 0)
{
//get hundredth, tenth, and single digit
int hundred = num / 100;
num %= 100;
int tenth = num / 10;
int single = num % 10;

if (hundred)
s = s + less_ten[hundred] + " Hundred";

if (tenth)
{
if (tenth == 1)
{ //special handling, choose from less_twenty based on value of single
s += less_twenty[single];
return s;
}
else  s += less_hundred[tenth];

}
if (single)
s += less_ten[single];
}
return s;
}

string numberToWords(int num)
{
const static char* unit[] = { "", " Thousand", " Million", " Billion", " Triliion" };
int parts[5] = {0};
for(int i  = 0; i < 5; ++i)
{
parts[i] = num % 1000;
num /= 1000;
}
string s;
for(int i = 0; i < 5; ++i)
{
if(parts[i] == 0) continue;
s = helper(parts[i]) + unit[i] + s;
}
s = s.size() ? s.substr(1) : "Zero";//substr(1)是为了去掉s首位的空格
return s;
}
};