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.

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)”.

Thoughts:

One annoying point is that integer overflow, so the solution below is using long instead of integer.

Using a HashMap to store remainder so that we could know if a same remainder exists.

Solutions:

``````public class Solution {
public String fractionToDecimal(int numerator, int denominator) {
long n = numerator, d = denominator;
if (n % d == 0) {
return n / d + "";
}
boolean neg = false;
if ((n < 0 && d > 0) || (n > 0 && d < 0)) {
neg = true;
}
if (n < 0) {
n = -n;
}
if (d < 0) {
d = -d;
}
HashMap<Long, Integer> index = new HashMap<Long, Integer>();
String result = "";
result += n / d + ".";
n = n % d;
while (n != 0) {
if (index.containsKey(n)) {
//recurring
result = result.substring(0, index.get(n)) + "(" + result.substring(index.get(n)) + ")";
break;
}
index.put(n, result.length());
result += n*10/d;
n = n*10 % d;
}
if (neg == true) {
result = '-' + result;
}
return result;
}
}
``````