166. Fraction to Recurring Decimal

Problem

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.

Example 1:

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

Example 2:

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

Example 3:

Input: numerator = 2, denominator = 3
Output: "0.(6)"

Solution

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

  var sign = numerator !== 0 && ((numerator > 0) ^ (denominator > 0));
  var num = Math.abs(numerator);
  var de = Math.abs(denominator);
  var result = sign ? '-' : '';
  var map = {};

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

  if (num === 0) return result;

  result += '.';

  while (num > 0) {
    num *= 10;

    if (map[num] !== undefined) {
      result = result.substr(0, map[num]) + '(' + result.substr(map[num]) + ')';
      break;
    } else {
      map[num] = result.length;
    }

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

  return result;
};

Explain:

nope.

Complexity:

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