Leetcode | Roman to Integer & Integer to Roman

Roman to Integer

Given a roman numeral, convert it to an integer.

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

搜了一下，才知道这道题可以写这么简洁。

class Solution {
public:
    int romanToInt(string s) {
        if (s.empty()) return 0;
        int dict[100];
        dict['I'] = 1; dict['V'] = 5; dict['X'] = 10; dict['L'] = 50;
        dict['C'] = 100; dict['D'] = 500; dict['M'] = 1000;
    
        int ans = dict[s[0]];
        for (int i = 1; i < s.length(); ++i) {
            if (dict[s[i]] <= dict[s[i - 1]]) {
                ans += dict[s[i]];
            } else {
                ans = ans - 2 * dict[s[i - 1]] + dict[s[i]];
            }
        }
        return ans;
    }
};

Integer to Roman

Given an integer, convert it to a roman numeral.

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

class Solution {
public:
    string intToRoman(int num) {
        string str[] = {"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 ret = "";
        for (int i = 0; i < 13; ++i) {
            while (num >= value[i]) {
                ret += str[i];
                num -= value[i];
            }
        }
        return ret;
    }
};