My easy java solution.

  • 4

    I assume that the input string is always a valid roman numerals. From the definition of the roman numerals, a letter subtracts only when the letter placed before another of greater value (thus XC or xc is 90). Otherwise, do addition. Thus, only check if we need to do subtractions or not.

    public int romanToInt(String s) {
        char[] romans = s.toCharArray();
        int sum = 0;
        for(int i=0; i<romans.length; i++){
            if(i<romans.length-1 && getNums(romans[i]) < getNums(romans[i+1]))
        return sum;
    public int getNums(char c){
            return 1;
        else if(c=='V')
            return 5;
        else if(c=='X')
            return 10;
        else if(c=='L')
            return 50;
        else if(c=='C')
            return 100;
        else if(c=='D')
            return 500;
            return 1000;

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