# 13. Roman to Integer （JAVA)

Roman numerals are represented by seven different symbols: `I``V``X``L``C``D` and `M`.

`Symbol       ValueI             1V             5X             10L             50C             100D             500M             1000`

For example, two is written as `II` in Roman numeral, just two one’s added together. Twelve is written as, `XII`, which is simply `X` + `II`. The number twenty seven is written as `XXVII`, which is `XX` + `V` + `II`.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not `IIII`. Instead, the number four is written as `IV`. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as `IX`. There are six instances where subtraction is used:

• `I` can be placed before `V` (5) and `X` (10) to make 4 and 9.
• `X` can be placed before `L` (50) and `C` (100) to make 40 and 90.
• `C` can be placed before `D` (500) and `M` (1000) to make 400 and 900.

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

Example 1:

`Input: "III"Output: 3`

Example 2:

`Input: "IV"Output: 4`

Example 3:

`Input: "IX"Output: 9`

Example 4:

`Input: "LVIII"Output: 58Explanation: L = 50, V= 5, III = 3.`

Example 5:

`Input: "MCMXCIV"Output: 1994Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.`
`class Solution {    public int romanToInt(String s) {        String sym = "MDCLXVI";        int[] val = {1000,500,100,50,10,5,1};        int num = 0;        int p; //array pointer        for(int i = 0; i < s.length(); i++){            p = sym.indexOf(s.charAt(i));            if(i+1 < s.length() && sym.indexOf(s.charAt(i+1)) < p){                num = num + val[sym.indexOf(s.charAt(i+1))] - val[p];                i++;            }            else{                num += val[p];            }        }        return num;    }}` 