【Leetcode 166】 Fraction to Recurring Decimal

標籤：

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: 長除法

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

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

　　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