166.Fraction-to-Recurring-Decimal

166. Fraction to Recurring Decimal

题目地址

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.
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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

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();
}
}