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)".

 

Credits:
Special thanks to @Shangrila for adding this problem and creating all test cases.

注意溢出：特例-2147483648, 1 | -1, -2147483648 | 

1. string to_string(long long n) {
2. stringstream ss;
3. ss<<n;
4. string result;
5. ss>>result;
6. return result;
7. }
8. string fractionToDecimal(int numerator, int denominator) {
10. if(numerator == 0) return "0";
11. string result;
12. if(numerator<0 ^ denominator<0) result += '-';
13. long long n = numerator, d = denominator;
14. n = abs(n);
15. d = abs(d);
16. result += to_string(n/d);
17. long long r = n%d;
18. if(r == 0) return result;
19. else result += '.';
20. unordered_map<int,int> exist;
21. while(r!=0) {
22. if(exist.find(r) != exist.end()) {
23. result.insert(exist[r],1,'(');
24. result += ')';
25. break;
26. }
27. exist[r] = result.size();
28. r *= 10;
29. result += to_string(r/d);
30. r = r % d;
31. }
32. return result;
33. }