166. Fraction to Recurring Decimal

166. 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.

  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)”.

• 题目大意：分数计算，除不尽的部分用（）表示

• 代码

  package HashTable;
  
  import sun.rmi.runtime.Log;
  
  import java.util.HashMap;
  import java.util.Map;
  
  /**
  * @author OovEver
  * 2018/1/14 16:48
  */
  public class LeetCode166 {
    public String fractionToDecimal(int numerator, int denominator) {
        if (numerator == 0) {
            return "0";
        }
        StringBuilder res = new StringBuilder();
        res.append((numerator > 0) ^ (denominator > 0) ? "-" : "");
        long num = Math.abs((long) numerator);
        long den = Math.abs((long) denominator);
        res.append(num / den);
        num %= den;
        if (num == 0) {
            return res.toString();
        }
        Map map = new HashMap<>();
        res.append(".");
        map.put(num, res.length());
        while (num != 0) {
            num *= 10;
            res.append(num / den);
            num %= den;
            if (map.containsKey(num)) {
                int index = map.get(num);
                res.insert(index, "(");
                res.append(")");
                break;
            } else {
                map.put(num, res.length());
            }
  
        }
        return res.toString();
  
    }
  }