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)".

摹擬小數除法，狂WA不止，還是不夠細！

1. 斟酌結果正負，

2. 全部轉為正數，由于負數會不便于中間處理，

3.用map保存余數和商對應位置的關系，出現重復余數直接插入括號結束.

4. 用longlong，INT_MIN變成正值會炸

5. 我用stringstream進行數轉string，看到有人這么做：

res += to_string(integral); 學到了

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;
    }
};

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