Leetcode 166 Fraction to Recurring Decimal

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)".

分数转小数。

模拟小数除法，狂WA不止，还是不够细！

1. 考虑结果正负，

2. 全部转为正数，因为负数会不便于中间处理，

3.用map保存余数和商对应位置的关系，出现重复余数直接插入括号结束.

4. 用longlong，INT_MIN变成正值会炸

5. 我用stringstream进行数转string，看到有人这么做：

res += to_string(integral); 学到了

class Solution {public:    string fractionToDecimal(int numerator1, int denominator1) {        long long numerator = numerator1>0 ? numerator1 : -(long long)numerator1;        long long denominator = denominator1>0 ? denominator1 : -(long long)denominator1;        string res;        stringstream s;        s << numerator / denominator;        s >> res;        if((long long)numerator1 * denominator1 < 0) res='-'+res;        numerator = numerator % denominator;        if(numerator)        {            res+=".";            unordered_map<int, int> mp;            while(numerator)            {                 if(mp.find(numerator) != mp.end())                {                    res.insert(mp[numerator], 1, '(');                    res += ")";                    break;                }                mp[numerator] = res.size();                numerator*=10;                int digit = numerator / denominator;                numerator%=denominator;                string add;                stringstream ss;                ss << digit;                ss >> add;                res += add;                            }        }        return res;    }};