166. Fraction To Recurring Decimal¶

Difficulty: Medium

166. Fraction to Recurring Decimal

Medium

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.

If multiple answers are possible, return any of them.

It is guaranteed that the length of the answer string is less than 10⁴ for all the given inputs.

Example 1:

Input: numerator = 1, denominator = 2
Output: "0.5"

Example 2:

Input: numerator = 2, denominator = 1
Output: "2"

Example 3:

Input: numerator = 4, denominator = 333
Output: "0.(012)"

Constraints:

-2³¹ <= numerator, denominator <= 2³¹ - 1
denominator != 0

Solution¶

class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        if (numerator == 0) 
            return "0";

        StringBuilder result = new StringBuilder();

        if ((numerator < 0) ^ (denominator < 0)) 
            result.append("-");

        long num = Math.abs((long) numerator);
        long den = Math.abs((long) denominator);

        result.append(num / den);
        long remainder = num % den;

        if (remainder == 0) 
            return result.toString();
        result.append(".");
        Map<Long, Integer> map = new HashMap<>();
        while (remainder != 0) {
            if (map.containsKey(remainder)) {
                int index = map.get(remainder);
                result.insert(index, "(");
                result.append(")");
                break;
            }
            map.put(remainder, result.length());
            remainder *= 10;
            result.append(remainder / den);
            remainder %= den;
        }
        return result.toString();
    }
}

Complexity Analysis¶

Time Complexity: O(?)
Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here