13. Roman to Integer

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Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

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Solution:

Tips:

implement it using recursion, just for practice it.

Java Code:

public class Solution {    public int romanToInt(String s) {        // I/1 V/5 X/10 L/50 C/100 D/500 M/1000        Map<Character, Integer> table = new HashMap<>();        table.put('I', 1);        table.put('V', 5);        table.put('X', 10);        table.put('L', 50);        table.put('C', 100);        table.put('D', 500);        table.put('M', 1000);                return romanToInt(s, 0, table);    }        public int romanToInt(String s, int begin, Map<Character, Integer> table) {        // I/1 V/5 X/10 L/50 C/100 D/500 M/1000        // left only can keep one, rigth can keep two for V L D        if (begin + 1 == s.length()) {            return table.get(s.charAt(begin));        }        if (begin == s.length()) {            return 0;        }                int left = table.get(s.charAt(begin));        int right = table.get(s.charAt(begin + 1));                return left >= right ? left + romanToInt(s, begin + 1, table) : right - left + romanToInt(s, begin + 2, table);    }}

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