LeetCode: Integer to Roman

Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.

From wikipedia at http://en.wikipedia.org/wiki/Roman_numerals
Roman Numerals, as used today, are based on seven symbols:^[1]

Symbol	Value
I	1
V	5
X	10
L	50
C	100
D	500
M	1,000

Numbers are formed by combining symbols together and adding the values. So II is two ones, i.e. 2, and XIII is a ten and three ones, i.e. 13. There is no zero in this system, so 207, for example, is CCVII, using the symbols for two hundreds, a five and two ones. 1066 is MLXVI, one thousand, fifty and ten, a five and a one.
Symbols are placed from left to right in order of value, starting with the largest. However, in a few specific cases, to avoid four characters being repeated in succession (such as IIII or XXXX) these can be reduced using subtractive notation as follows:

• the numeral I can be placed before V and X to make 4 units (IV) and 9 units (IX respectively)
• X can be placed before L and C to make 40 (XL) and 90 (XC respectively)
• C can be placed before D and M to make 400 (CD) and 900 (CM) according to the same pattern

An example using the above rules would be 1904: this is composed of 1 (one thousand), 9 (nine hundreds), 0 (zero tens), and 4 (four units). To write the Roman numeral, each of the non-zero digits should be treated separately. Thus 1,000 = M, 900 = CM, and 4 = IV. Therefore, 1904 is MCMIV.
Below are some examples of the modern use of Roman Numerals.

• 1954 as MCMLIV (Trailer for the movie The Last Time I Saw Paris)
• 1990 as MCMXC (The title of musical project Enigma's debut album MCMXC a.D., named after the year of its release.)
• 2014 as MMXIV - the year of the games of the XXII (22nd, Winter) Olympiad (in Sochi)

Solution

The solution takes advantage of string(int n, char c) instructor in C++, fill n consecutive copies of character c