Notes:
1. When numerator is 0, return "0". Check this corner case, because 0 / -5 will return -0.
2. Use long long int for divd and divs, mainly for divs. Because when divs = INT_MIN, fabs(divs) is large.
3. Do not forget to rest *= 10 to get the next level.
1 class Solution { 2 public: 3 string fractionToDecimal(int numerator, int denominator) { 4 if (numerator == 0) return "0"; 5 string result; 6 if (numerator < 0 ^ denominator < 0) result = "-"; 7 long long int divd = fabs(numerator), divs = fabs(denominator), rest = divd % divs; 8 result += to_string(divd / divs); 9 if (rest == 0) { 10 return result; 11 } 12 result += '.'; 13 unordered_map<int, int> mapping; 14 while (rest > 0) { 15 if (mapping.find(rest) != mapping.end()) { 16 result.insert(mapping[rest], "("); 17 result += ')'; 18 return result; 19 } 20 mapping[rest] = result.size(); 21 rest *= 10; 22 result += to_string(rest/divs); 23 rest %= divs; 24 } 25 return result; 26 } 27 };
