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# 166.Fraction-to-Recurring-Decimal

## 166. Fraction to Recurring Decimal

## 题目地址

<https://leetcode.com/problems/fraction-to-recurring-decimal/>

## 题目描述

```
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)"
```

## 代码

### Approach #1 Long Division

```java
class Solution {
  public String fractionToDecimal(int numerator, int denominator) {
        if (numberator == 0)        return "0";
    StringBuilder fraction = new StringBuilder();
    if (numberator < 0 ^ denominator < 0) {
      fraction.append("-");
    }

    long dividend = Math.abs(Long.valueOf(numberator));
    long divisor = Math.abs(Long.valueOf(denominator));
    fraction.append(String.valueOf(dividend / divisor));
    long remainder = dividend % divisor;
    if (remainder == 0) {
      return fraction.toString();
    }
    fraction.append(".");
    Map<Long, Integer> map = new HashMap();
    while (remainder != 0) {
      if (map.containsKey(remainder)) {
        fraction.insert(map.get(remainder), "(");
        fraction.append(")");
        break;
      }
      map.put(remainder, fraction.length());
      remainder *= 10;
      fraction.append(String.valueOf(remainder / divisor));
      remainder %= divisor;
    }

    return fraction.toString();
  }
}
```