Roman to Integer Cont(2)…

Question: Given String value of a Roman numeral, compute and return the integer equivalent. Find the full question here.

And in case you are just starting off, you might want to take a look at the initial approach posted here and may be here.

Approach 3: Well, we are borrowing the fundamental ideas from the previous approaches of course. But we are trying to implement the lookup in a different way. This is definitely boosting our run-time by leaps and bounds. The look up is implemented using static map with a static anonymous block for initialization.

Let’s dive into the code straight away —

//Approach 3
//Runtime: 4ms
//Memory usage: 37.2MB
class Solution {
    private static HashMap<Character, Integer> map = new HashMap<>();
    
    static {
        map.put('M', 1000);
        map.put('D', 500);
        map.put('C', 100);
        map.put('L', 50);
        map.put('X', 10);
        map.put('V', 5);
        map.put('I', 1);
    }
    
 public int romanToInt(String s) {
        char[] roman = s.toCharArray();
        int finalInt = 0;
        int curr = map.get(roman[0]);
        int next = 0;
        for(int i = 0; i<roman.length-1; i++) {
            next =map.get(roman[i+1]);
            if(curr>=next) {
          finalInt+=curr;
         }else {
          finalInt-=curr;
         }
            curr = next;
        }
        return finalInt+curr;
    }
}

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Cheers & Chao!