leetcode21: Integer to Roman

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

my reminders: string is different vector, which can use position instead of iterator to assign a element. because string's element is char but vector is templete. also string can insert or operate char*, char and string as arguments.

 

class Solution {
public:
    string intToRoman(int num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        const char* table[4][10] =
        {
            "", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX",
            "", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC",
            "", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM",
            "", "M", "MM", "MMM", "  ", " ", "  ", "   ", "    ", "  "
        };
        
        if( num < 0 || num >3999) return "";
        
        int digit = 0;
        string rel;
        while( num  != 0) {
            rel.insert( 0,  table[digit++][ num%10] );
            num /=10;
        }
        
        return rel;
        
    }
};