Given a string, s, representing a Roman numeral, return the integer value of the Roman numeral.

Seven different symbols represent Roman numerals:

So, in Roman numerals, $2$ is written as $\text {II}$, which is simply two $1$s added together. The number$12$ is written as $\text{XII}$, which is simply $\text{X} + \text{II}$. The number $27$ is written as $\text{XXVII}$, which breaks down into $\text{XX} + \text{V} + \text{II}$.

Roman numerals are usually written from largest to smallest from left to right ($\text{X}$) comes first, and then $\text I$ for $12$). However, there are six cases where a smaller numeral is placed before a larger one to indicate subtraction. For example, the number $4$ is written as $\text{IV}$, because the $1$ comes before the $5$, so we subtract it to get $4$. The remaining such cases are as follows:

1. $\text{IV}$ ($5$ – $1$) = $4$

2. $\text{IX}$ ($10$ – $1$) = $9$

3. $\text{XL}$ ($50$ – $10$) = $40$

4. $\text{XC}$ ($100$ – $10$) = $90$

5. $\text{CD}$ ($500$ – $100$) = $400$

6. $\text{CM}$ ($1000$ – $100$) = $900$

Constraints:

• $1 \leq$ s.length $\leq 15$

• s contains only the characters ‘$\text{I}$’, ‘$\text V$’, ‘$\text X$’, ‘$\text L$’, ‘$\text C$’, ‘$\text D$’, and ‘$\text M$’.

• It is guaranteed that s is a valid Roman numeral in the range [$1$, $3999$].

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.