166. Fraction to Recurring Decimal

標籤：pre   str   close   parent   while   action   長度   put   除法   

Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.

If the fractional part is repeating, enclose the repeating part in parentheses.

Example 1:

Input: numerator = 1, denominator = 2
Output: "0.5"

Example 2:

Input: numerator = 2, denominator = 1
Output: "2"

Example 3:

Input: numerator = 2, denominator = 3
Output: "0.(6)"

class Solution:    def fractionToDecimal(self, numerator, denominator):        """        :type numerator: int        :type denominator: int        :rtype: str        """        negative = False        if numerator*denominator<0:            negative = True        n,m = abs(numerator),abs(denominator)        a = n//m        if a==n/m:            if negative:                return ‘-‘+str(a)            else:                return str(a)        temp = []        res = []        n = n%m        while True:            temp.append(n)            n *= 10            res.append(str(n//m))            n = n%m            if n==0:                if negative:                    return ‘-‘ + str(a) + ‘.‘ + ‘‘.join(res)                else:                    return str(a) + ‘.‘ + ‘‘.join(res)            if n in temp:                if negative:                    return ‘-‘ + str(a) + ‘.‘ + ‘‘.join(res[:temp.index(n)]) + ‘(‘ + ‘‘.join(res[temp.index(n):]) + ‘)‘                else:                    return str(a) + ‘.‘ + ‘‘.join(res[:temp.index(n)]) + ‘(‘ + ‘‘.join(res[temp.index(n):]) + ‘)‘

剛開始的思路是從商中找出迴圈體，這樣的問題是由於不確定迴圈體長度和開始的位置，很難判斷。但如果用除法的方式，從被除數中找出迴圈體就很簡單了。

166. Fraction to Recurring Decimal