leetcode-algorithms/src/RomanToInteger.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

41 lines (37 loc) · 1.14 KB

// https://leetcode.com/problems/roman-to-integer

// T: O(|S|)

// S: O(1)

import java.util.Map;

import java.util.Set;

public class RomanToInteger {

private static final Map<Character, Integer> ROMAN_NUMERALS = Map.of(

'I', 1,

'V', 5,

'X', 10,

'L', 50,

'C', 100,

'D', 500,

'M', 1000

);

private static final Map<Character, Set<Character>> DECREMENT_ROMAN_NUMERALS = Map.of(

'I', Set.of('V', 'X'),

'X', Set.of('L', 'C'),

'C', Set.of('D', 'M')

);

public int romanToInt(String s) {

int number = 0;

for (int i = 0 ; i < s.length() ; ) {

final char c = s.charAt(i);

if (DECREMENT_ROMAN_NUMERALS.containsKey(c)

&& i + 1 < s.length()

&& DECREMENT_ROMAN_NUMERALS.get(c).contains(s.charAt(i + 1))) {

number += ROMAN_NUMERALS.get(s.charAt(i + 1)) - ROMAN_NUMERALS.get(c);

i += 2;

} else {

number += ROMAN_NUMERALS.get(c);

i++;

}

return number;

}

Expand file tree