166. Fraction to Recurring Decimal

Description

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

 

Solutions

Solution: Hash Map

• Time complexity: O(n)
• Space complexity: O(n)

 

JavaScript

/**
 * @param {number} numerator
 * @param {number} denominator
 * @return {string}
 */
const fractionToDecimal = function (numerator, denominator) {
  if (numerator === 0) return '0';

  let result = '';

  if (Math.sign(numerator) !== Math.sign(denominator)) {
    result += '-';
  }

  const den = Math.abs(denominator);
  let num = Math.abs(numerator);

  result += Math.floor(num / den);
  num %= den;

  if (num === 0) return result;

  const numMap = new Map();

  result += '.';

  while (num) {
    if (numMap.has(num)) {
      const index = numMap.get(num);

      return `${result.slice(0, index)}(${result.slice(index)})`;
    }

    numMap.set(num, result.length);
    num *= 10;
    result += Math.floor(num / den);
    num %= den;
  }

  return result;
};