Equal Rational Numbers

Given two strings S and T, each of which represents a non-negative rational number, return True if and only if they represent the same number. The strings may use parentheses to denote the repeating part of the rational number.

In general a rational number can be represented using up to three parts: an integer part, a non-repeating part, and a repeating part. The number will be represented in one of the following three ways:

The repeating portion of a decimal expansion is conventionally denoted within a pair of round brackets.  For example:

1 / 6 = 0.16666666... = 0.1(6) = 0.1666(6) = 0.166(66)

Both 0.1(6) or 0.1666(6) or 0.166(66) are correct representations of 1 / 6.

 

Example 1:

Input: S = "0.(52)", T = "0.5(25)"
Output: true
Explanation:
Because "0.(52)" represents 0.52525252..., and "0.5(25)" represents 0.52525252525..... , the strings represent the same number.
Example 2:

Input: S = "0.1666(6)", T = "0.166(66)"
Output: true
Example 3:

Input: S = "0.9(9)", T = "1."
Output: true
Explanation: 
"0.9(9)" represents 0.999999999... repeated forever, which equals 1.  [See this link for an explanation.]
"1." represents the number 1, which is formed correctly: (IntegerPart) = "1" and (NonRepeatingPart) = "".
 

Note:

  1. Each part consists only of digits.
  2. The <IntegerPart> will not begin with 2 or more zeros.  (There is no other restriction on the digits of each part.)
  3. 1 <= <IntegerPart>.length <= 4
  4. 0 <= <NonRepeatingPart>.length <= 4
  5. 1 <= <RepeatingPart>.length <= 4

Solution:

class Solution {
    public boolean isRationalEqual(String S, String T) {
        return f(S) == f(T);
    }
    
    private double f(String s) {
        int idx = s.indexOf("(");
        if (idx > 0) {
            String base = s.substring(0, idx);
            String repeat = s.substring(idx + 1, s.length() - 1);
            for (int i = 0; i < 20; i ++) {
                base += repeat;
            }
            return Double.valueOf(base);
        }
        return Double.valueOf(s);
    }
}