java 13. Roman to Integer（＃）。java

Posted 2021-05-08

"""
Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.
"""
class Solution(object):
    def romanToInt(self, s):
        """
        :type s: str
        :rtype: int
        """
        numerals = {
            'M' : 1000,
            'D' : 500,
            'C' : 100,
            'L' : 50,
            'X' : 10,
            'V' : 5,
            'I' : 1
            
        }
        
        res = 0;
        for i in range(len(s)):
            res += numerals[s[i]];
            if i > 0 and numerals[s[i]] > numerals[s[i-1]]:
                res -= numerals[s[i-1]] * 2;
        return res;

public class Solution {
    public int romanToInt(String s) {
        int nums[]=new int[s.length()];
        for(int i=0; i<s.length(); i++){
            switch (s.charAt(i)){
                case 'M':
                    nums[i]=1000;
                    break;
                case 'D':
                    nums[i]=500;
                    break;
                case 'C':
                    nums[i]=100;
                    break;
                case 'L':
                    nums[i]=50;
                    break;
                case 'X' :
                    nums[i]=10;
                    break;
                case 'V':
                    nums[i]=5;
                    break;
                case 'I':
                    nums[i]=1;
                    break;
            }
        }
        int sum=0;
        for(int i=0; i<nums.length-1; i++){
            if(nums[i] < nums[i+1])
                sum-=nums[i];
            else
                sum+=nums[i];
        }
        return sum+nums[nums.length-1];
    }
}

public class Solution {
    public int romanToInt(String s) {
        char[] sc = s.toCharArray();
        int sum = 0;
        for (int index = sc.length - 1; index >= 0; index--) {
            if (sc[index] == 'I') {
                sum += (sum < 5 ? 1 : -1);
            } else if (sc[index] == 'V') {
                sum += 5;
            } else if (sc[index] == 'X') {
                sum += (sum < 50 ? 10 : -10);
            } else if (sc[index] == 'L') {
                sum += 50;
            } else if (sc[index] == 'C') {
                sum += (sum < 500 ? 100 : -100);
            } else if (sc[index] == 'D') {
                sum += 500;
            } else if (sc[index] == 'M') {
                sum += 1000;
            }
        }
        return sum;
    }
}

public class Solution {
    public int romanToInt(String s) {
        Map<Character, Integer> map = new HashMap<Character, Integer>(){{
            put('M', 1000);
            put('D', 500);
            put('C', 100);
            put('L', 50);
            put('X', 10);
            put('V', 5);
            put('I', 1);
        }};
        int sum = 0;
        sum += map.get(s.charAt(0));
        for(int i = 1; i < s.length(); i++){
            sum += map.get(s.charAt(i));
            if(map.get(s.charAt(i)) > map.get(s.charAt(i - 1)))
                sum -= map.get(s.charAt(i - 1)) * 2;
        }
        return sum;
    }
}