[LeetCode 13] Roman to Integer

문제 바로가기

Description

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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

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• Input: s = “III”
• Output: 3
• Explanation: III = 3.

Example 2

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• Input: s = “LVIII”
• Output: 58
• Explanation: L = 50, V= 5, III = 3.

Example 3

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• Input: s = “MCMXCIV”
• Output: 1994
• Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

Constraints

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• 1 <= s.length <= 15
• s contains only the characters ('I', 'V', 'X', 'L', 'C', 'D', 'M').
• It is guaranteed that s is a valid roman numeral in the range [1, 3999].

Hint

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Hint 1

  Problem is simpler to solve by working the string from back to front and using a map.
	

Code

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내 제출

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class Solution {
    public int romanToInt(String s) {
        int result = 0;
        char[] str = s.toCharArray();

        for (char c : str) {
            switch (c) {
                case 'I':
                    result += 1;
                    break;
                case 'V':
                    result += 5;
                    break;
                case 'X':
                    result += 10;
                    break;
                case 'L':
                    result += 50;
                    break;
                case 'C':
                    result += 100;
                    break;
                case 'D':
                    result += 500;
                    break;
                case 'M':
                    result += 1000;
                    break;
            }
        }
        //bw.write("for문 나온 후 : " + result + "\n");

        if (s.contains("IV")) {
            result -= 6;
            result += 4;
        }
        if (s.contains("IX")) {
            result -= 11;
            result += 9;
        }
        if (s.contains("XL")) {
            result -= 60;
            result += 40;
        }
        if (s.contains("XC")) {
            result -= 110;
            result += 90;
        }
        if (s.contains("CD")) {
            result -= 600;
            result += 400;
        }
        if (s.contains("CM")) {
            result -= 1100;
            result += 900;
        }
        //bw.write("if문 나온 후 : " + result);
        return result;
    }
}

Runtime	Memory
3 ms	44.7 MB

다른 풀이

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class Solution {
    public int romanToInt(String s) {
        int value=0,curr=roman(s.charAt(0));
        for(int i=1;i<s.length();i++)
        {
            int next=roman(s.charAt(i));
            if(curr<next)
                value-=curr;
            else
                value+=curr;
            curr=next;
        }
        return value+roman(s.charAt(s.length()-1));
    }

    int roman(char c)
    {
        switch(c)
        {
            case 'I':return 1;
            case 'V':return 5;
            case 'X':return 10;
            case 'L':return 50;
            case 'C':return 100;
            case 'D':return 500;
            case 'M':return 1000;
            default: return 0;
        }
    }
}

Reference

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