LeetCode -- Roman to Integer

Given a roman numeral, convert it to an integer.

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

Given a roman number, convert it into an integer.

Convert a string of numbers to a character array. In the following table, each number corresponds to only one character, and the characters are different. Therefore, the values can be matched from the beginning.

The Roman Symbols

The Romans used a special method of showing numbers, based on the following symbols:

1	5	10	50	100	500	1000
I	V	X	L	C	D	M

public int romanToInt(String s) {Map
 
   romans = new HashMap
  
   ();romans.put('I', 1);romans.put('V', 5);romans.put('X', 10);romans.put('L', 50);romans.put('C', 100);romans.put('D', 500);romans.put('M', 1000);char[] ch = s.toCharArray();int num = 0, val = 0;for (int i = 0; i < ch.length; i++) {val = romans.get(ch[i]);if (i == ch.length - 1 || romans.get(ch[i + 1]) <= val)num += val;elsenum -= val;}return num;}
  
 

Reference: http://www.mathsisfun.com/roman-numerals.html