[LeetCode] 166. Fraction to Recurring Decimal

Problem : https://leetcode.com/problems/fraction-to-recurring-decimal/

Simulator long division process to calculate fraction result.

Because the same numerator always leads to the same fraction result. 

Use hash table to save numerator encountered to avoid repeating fractional part.

class Solution:
    def fractionToDecimal(self, numerator: int, denominator: int) -> str:
        negative = (numerator < 0) ^ (denominator < 0)
        
        numerator = abs(numerator)
        denominator = abs(denominator)
        
        result = str(numerator // denominator)
        
        if numerator % denominator == 0:
            return "-" + result if negative and numerator != 0  else result
        
        numerator = numerator % denominator
        numerator *= 10
        
        visited = {}
        
        result += "."
        
        while numerator > 0:
            
            if numerator not in visited:
                visited[numerator] = len(result)
            else:
                prefix = result[:visited[numerator]] + '('
                appendix = result[visited[numerator]:] + ')'
                result = prefix + appendix
                break
            
            if numerator > denominator:
                result += str(numerator // denominator)
                numerator = numerator % denominator
            else:
                result += '0'
            
            numerator *= 10
        
        return "-" + result if negative else result

Edited on 03/04/2021. A simpler implementation.