LeetCode 13. Roman to Integer -- 罗马数字转整数

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

public class Main {
//罗马数字表示法，基本字符有7个：I，V，X，L，C，D，M，分别表示1，5，10，50，100，500，1000。
public int romanToInt(String s) {
int sum = 0;
//先减去2倍，后面再遇到时每一位都是再加一次，所以还是减去了一次。相减的情况只有以下6种情况。
if (s.indexOf("IV") != -1) sum -= 2;
if (s.indexOf("IX") != -1) sum -= 2;
if (s.indexOf("XL") != -1) sum -= 20;
if (s.indexOf("XC") != -1) sum -= 20;
if (s.indexOf("CD") != -1) sum -= 200;
if (s.indexOf("CM") != -1) sum -= 200;

char[] c = s.toCharArray();
for (int i = 0; i < s.length(); i++) {
if (c[i] == 'I') sum += 1;
if (c[i] == 'V') sum += 5;
if (c[i] == 'X') sum += 10;
if (c[i] == 'L') sum += 50;
if (c[i] == 'C') sum += 100;
if (c[i] == 'D') sum += 500;
if (c[i] == 'M') sum += 1000;
}
return sum;
}//romanToInt

public static void main(String[] args) {
System.out.println(new Main().romanToInt("XXX"));//30
System.out.println(new Main().romanToInt("IVXX"));//24
System.out.println(new Main().romanToInt("IXXX"));//29
System.out.println(new Main().romanToInt("CDCXXI"));//521
}
}

3999 / 3999 test cases passed.

Status: Accepted

Runtime: 89 ms

Your runtime beats 93.16 % of java submissions.