[leetcode]Fraction to Recurring Decimal-优快云博客

本文提供了一种将任意两个整数表示的分数转换为字符串格式的方法，特别针对循环小数部分进行了详细说明。通过使用Java实现的算法，能够有效地处理循环节并将其括在括号中。

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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;
}