package leetCode_13;

import java.util.HashMap;

/**

* @author dimdark

* @date 2017-10-06

* @time 4:53 PM

*/

public class Solution {

private static HashMap<Character, Integer> romanMap = new HashMap<Character, Integer>();

private static final String ROMAN_STRING = "IVXLCDM";

static {

romanMap.put('I', 1);

romanMap.put('V', 5);

romanMap.put('X', 10);

romanMap.put('L', 50);

romanMap.put('C', 100);

romanMap.put('D', 500);

romanMap.put('M', 1000);

}

public int romanToInt(String s) {

if (s == null || s.length() == 0) return 0;

char[] cs = s.toCharArray();

int rst = romanMap.get(cs[cs.length - 1]);

int i = cs.length - 2, j = cs.length - 1;

while (i >= 0) { // O(n)

int idx1 = ROMAN_STRING.indexOf(cs[i]);

int idx2 = ROMAN_STRING.indexOf(cs[j]);

if (idx1 >= idx2) {

rst += romanMap.get(cs[i]);

} else {

rst -= romanMap.get(cs[i]);

}

--i; --j;

}

return rst;

}

}