[leetcode]Fraction to Recurring Decimal

各种情况。有恶心的负数最值，用long long来做了。除此之外的情况下面都列出来了。

/*

1, 8 = 0.125

1, 6 = 0.1(6)

-50, 6 = -6.25

0, -3 = 0

-1, -2147483648 = "0.0000000004656612873077392578125"

*/

typedef long long llong;



class Solution {

public:

    string fractionToDecimal(int numerator, int denominator) {

        if (numerator == 0) {

            return "0";

        }

        string result;

        llong n = numerator;

        llong d = denominator;

        if(n < 0 ^ d < 0 ) result+='-'; 

        n = abs(n);

        d = abs(d);

        result += to_string(n / d);

        llong r = n % d;

        if (r == 0) {

            return result;

        } else {

            result += '.';

        }

        unordered_map<int, int> map;

        while (r != 0) {

            if (map.find(r) != map.end()) {

                result.insert(map[r], 1, '(');

                result += ')';

                break;

            }

            map[r] = result.size();

            r *= 10;

            result += to_string(r / d);

            r %= d;

        }

        return result;

    }

};