LeetCode in Kotlin

972. Equal Rational Numbers

Hard

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.

A rational number can be represented using up to three parts: <IntegerPart>, <NonRepeatingPart>, and a <RepeatingPart>. The number will be represented in one of the following three ways:

• <IntegerPart>
  • For example, 12, 0, and 123.
• **<.>**</code>
  • For example, 0.5, 1., 2.12, and 123.0001.
• **<.>****<(>****<)>**</code>
  • For example, 0.1(6), 1.(9), 123.00(1212).

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).

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) = “”.

Constraints:

• Each part consists only of digits.
• The <IntegerPart> does not have leading zeros (except for the zero itself).
• 1 <= <IntegerPart>.length <= 4
• 0 <= <NonRepeatingPart>.length <= 4
• 1 <= <RepeatingPart>.length <= 4

Solution

import kotlin.math.abs
import kotlin.math.pow

class Solution {
    fun isRationalEqual(s: String, t: String): Boolean {
        return abs(valueOf(s) - valueOf(t)) < 1e-9
    }
    private val ratios = doubleArrayOf(1.0, 1.0 / 9, 1.0 / 99, 1.0 / 999, 1.0 / 9999)
    private fun valueOf(s: String): Double {
        if (!s.contains("(")) return java.lang.Double.valueOf(s)
        val integerNonRepeating = java.lang.Double.valueOf(s.substring(0, s.indexOf('(')))
        val nonRepeatingLength = s.indexOf('(') - s.indexOf('.') - 1
        val repeating = s.substring(s.indexOf('(') + 1, s.indexOf(')')).toInt()
        val repeatingLength = s.indexOf(')') - s.indexOf('(') - 1
        return integerNonRepeating +
            repeating * 0.1.pow(nonRepeatingLength.toDouble()) * ratios[repeatingLength]
    }
}

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