# Roman to Integer

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

```
Symbol
Value

I             1
V             5
X             10
L             50
C             100
D             500
M             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.&#x20;
* `X`can be placed before`L`(50) and`C`(100) to make 40 and 90.&#x20;
* `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

**Example 1:**

```
Input:
 "III"

Output:
 3
```

**Example 2:**

```
Input:
 "IV"

Output:
 4
```

**Example 3:**

```
Input:
 "IX"

Output:
 9
```

**Example 4:**

```
Input:
 "LVIII"

Output:
 58

Explanation:
 L = 50, V= 5, III = 3.
```

**Example 5:**

```
Input:
 "MCMXCIV"

Output:
 1994

Explanation:
 M = 1000, CM = 900, XC = 90 and IV = 4.
```

## Note

减去2/20/200，然后加对应的值

## Code

```java
class Solution {
    public int romanToInt(String s) {
        int sum = 0;
    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 < c.length; i++) {
        if(c[i] == 'M') sum+= 1000;
        if(c[i] == 'D') sum+= 500;
        if(c[i] == 'C') sum+= 100;
        if(c[i] == 'L') sum+= 50;
        if(c[i] == 'X') sum+= 10;
        if(c[i] == 'V') sum+= 5;
        if(c[i] == 'I') sum+= 1;
    }
    return sum;
    }
}
```
