q013_RomanToInteger.java

package leetcode_algorithm;

/**
Given a roman numeral, convert it to an integer.

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

public class q013_RomanToInteger {

    public static void main(String[] args) {
        System.out.println(romanToInt("I"));
        System.out.println(romanToInt("XI"));
        System.out.println(romanToInt("IV"));
        System.out.println(romanToInt("CCXXXIV"));
    }

    /**
     * ½â·¨1
     *
     * @param s
     * @return
     */
    public static int romanToInt(String s) {
        int nums[]=new int[s.length()];
        for(int i=0;i<s.length();i++){
            switch (s.charAt(i)){
                case 'M':
                    nums[i]=1000;
                    break;
                case 'D':
                    nums[i]=500;
                    break;
                case 'C':
                    nums[i]=100;
                    break;
                case 'L':
                    nums[i]=50;
                    break;
                case 'X' :
                    nums[i]=10;
                    break;
                case 'V':
                    nums[i]=5;
                    break;
                case 'I':
                    nums[i]=1;
                    break;
            }
        }
        int sum=0;
        for(int i=0;i<nums.length-1;i++){
            if(nums[i]<nums[i+1])
                sum-=nums[i];
            else
                sum+=nums[i];
        }
        return sum+nums[nums.length-1];
    }

}