文章标题

12. Integer to Roman

Given an integer, convert it to a roman numeral.

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



由上图可知，数字都可由1，4，5，9，10，40，50，90，100，400，500，900，1000构成；

string intToRoman(int num) {
string symbal[] = { "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };
int value[] = { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 };

string str = "";
for (int i = 0; num != 0; i++){
while (num >= value[i]){
str += symbal[i];
num -= value[i];
}
}
return str;
}

13. Roman to Integer

Given a roman numeral, convert it to an integer.

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

int romanToInt(string s) {
map<char, int> res = { { 'I', 1 }, { 'V', 5 }, { 'X', 10 }, { 'L', 50 },
{ 'C', 100 }, { 'D', 500 }, { 'M', 1000 } };

int sum = res[s[0]];
for (int i = 1; i < s.size(); i++){
if (res[s[i - 1]] < res[s[i]])
sum += res[s[i]] - 2 * res[s[i - 1]];
else
sum += res[s[i]];
}
return sum;
}