LC-romanToInteger.js

/*
Date Started: 03/07/2023
Language Used: JavaScript

Difficulty: Easy
Question 13. 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, 2 is written as II in Roman numeral, just two ones added together. 12 is written as XII, which is simply X + II. The number 27 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. 
X can be placed before L (50) and C (100) to make 40 and 90. 
C can be placed before D (500) and M (1000) to make 400 and 900.
Given a roman numeral, convert it to an integer.

 

Example 1:
Input: s = "III"
Output: 3
Explanation: III = 3.

Example 2:
Input: s = "LVIII"
Output: 58
Explanation: L = 50, V= 5, III = 3.

Example 3:
Input: s = "MCMXCIV"
Output: 1994
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
*/


function rToi(rom){
    // symbols object serves as a reference as to how much to add to the final answer
    const symbols = {
        'I': 1,
        'V': 5,
        'X': 10,
        'L': 50,
        'C': 100,
        'D': 500,
        'M': 1000,
    }
    // the array variable is storing the roman numeral split into an array
    const array = rom.split('')
    // answer variable stores the final answer
    let answer = 0
    // for loop iterating through each letter of the roman numeral array
    for(let i = 0; i < array.length; i++){
        // conditional statements checking for 'IV', 'IX', 'XL', 'XC', 'CD', 'CM'
        if(array[i] == 'I' && array[i+1] == 'V'){
            answer += 4
            i++
        }
        else if(array[i] == 'I' && array[i+1] == 'X'){
            answer += 9
            i++
        }
        else if(array[i] == 'X' && array[i+1] == 'L'){
            answer += 40
            i++
        }
        else if(array[i] == 'X' && array[i+1] == 'C'){
            answer += 90
            i++
        }
        else if(array[i] == 'C' && array[i+1] == 'D'){
            answer += 400
            i++
        }
        else if(array[i] == 'C' && array[i+1] == 'M'){
            answer += 900
            i++
        }
        else {
            // if the roman numeral matches a symbol in the symbols object it will add the value for that specific numeral
            answer += symbols[array[i]]
        }
    }
    return answer
}

/* 
Runtime: 128ms, Beats: 67%
Memory: 47.8MB, Beats: 30.69%
*/