LeetCode – Fraction to Recurring Decimal (Java)

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.

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)".

Java Solution

See internal comments in the code.

public String fractionToDecimal(int numerator, int denominator) {
	if (numerator == 0)
		return "0";
	if (denominator == 0)
		return "";
 
	String result = "";
 
	// is result is negative
	if ((numerator < 0) ^ (denominator < 0)) {
		result += "-";
	}
 
	// convert int to long
	long num = numerator, den = denominator;
	num = Math.abs(num);
	den = Math.abs(den);
 
	// quotient 
	long res = num / den;
	result += String.valueOf(res);
 
	// if remainder is 0, return result
	long remainder = (num % den) * 10;
	if (remainder == 0)
		return result;
 
	// right-hand side of decimal point
	HashMap<Long, Integer> map = new HashMap<Long, Integer>();
	result += ".";
	while (remainder != 0) {
		// if digits repeat
		if (map.containsKey(remainder)) {
			int beg = map.get(remainder); 
			String part1 = result.substring(0, beg);
			String part2 = result.substring(beg, result.length());
			result = part1 + "(" + part2 + ")";
			return result;
		}
 
		// continue
		map.put(remainder, result.length());
		res = remainder / den;
		result += String.valueOf(res);
		remainder = (remainder % den) * 10;
	}
 
	return result;
}
Category >> Algorithms >> Interview >> Java  
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  • Sreeparna Mukherjee

    Time limit is getting exceeded in the above code.

    long nume = Math.abs((long)numerator);

    long deno = Math.abs((long)denominator);

    String sign = (numerator < 0) ^ (denominator < 0) ? "-" : "";

    if (deno == 0) {

    return "";

    } else if (nume == 0) {

    return "0";

    } else if (nume % deno == 0) {

    return sign + nume/deno + "";

    }

    HashMap map = new HashMap();

    StringBuffer rst = new StringBuffer(sign + nume/deno + ".");

    long end = nume%deno * 10;//The decimal portion of the value, after decimal point

    int i = 0;

    while (end != 0){

    if (map.containsKey(end)) {

    rst.insert(rst.indexOf(".") + map.get(end) + 1, "(");

    rst.append(")");

    return rst.toString();

    }

    rst.append(end/deno);

    map.put(end, i++);

    end = (end % deno) * 10;

    }

    return rst.toString();

    }
    }