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【Leetcode 166】 Fraction to Recurring Decimal

Description:

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.

For example,

  • Given numerator = 1, denominator = 2, return "0.5".
  • Given numerator = 2, denominator = 1, return "2".
  • Given numerator = 2, denominator = 3, return "0.(6)".

Solution:

  long division: 长除法

  Trick: Determining whether two nums have different sign(+ or  -) can use follow codes:

if((n<0)^(d<0))  //异号orif((n>0)^(d>0))  //异号

  Above code avoiding product‘s value overflow.

Code:

class Solution {public:    string fractionToDecimal(int numerator, int denominator) {        if(!numerator) return "0";        long long n = numerator, d = denominator;        string ret = "";        if((n<0)^(d<0)) ret += -;        if(n < 0) n = -n;        if(d < 0) d = -d;        ret += to_string(n/d);        if(n % d == 0){            return ret;        }ret += .;        map<long long, int>hash;        for(long long r = n % d; r; r %= d){            if(hash.find(r) != hash.end()){                ret.insert(hash[r],"(");                ret += ")";                return ret;            }            hash[r] = ret.size();            r *= 10;            ret += to_string(r / d);        }    }};

 

【Leetcode 166】 Fraction to Recurring Decimal