Leetcode: Fraction to Recurring Decimal

标签：leetcode   无限循环小数   recurring decimal   

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)".

Solution:

1、用一个map来记录n除以d的过程中被除数的变化，以及当被除数为n时相应的商在返回结果string中的位置，方便以后添加（。

2、负数变正数的时候会越界，下面的例子2^31 = 2 147 483 648，int表示范围（-2147483648~2147483647），所以要用long long：

Input:-1, -2147483648

Output:"0.0000000000000000000000000000001"

Expected:"0.0000000004656612873077392578125"

class Solution {
public:
	string fractionToDecimal(int numerator, int denominator) {
		string res = "";
		if (numerator == 0) return "0";
		if (denominator == 0)return res;

		long long n = numerator;
		long long d = denominator;
		if ((n < 0 && d > 0) || (n > 0 && d < 0))
			res = "-";
		if (n < 0) n = -n;
		if (d < 0) d = -d;
		res += to_string(n / d);
		n = n%d;
		if (n == 0) return res;
		res += '.';

		int pos = res.size();
		map<long long, int> record;
		while (n != 0) {
			if (record.find(n) != record.end()) {
				res.insert(res.begin() + record[n], '(');
				res += ')';
				return res;
			}
			record[n] = pos;
			res += char(n * 10 / d + '0');
			pos++;
			n = (n * 10) % d;
		}
		return res;
	}
};

Leetcode: Fraction to Recurring Decimal

标签：leetcode   无限循环小数   recurring decimal   

原文地址：http://blog.csdn.net/doc_sgl/article/details/43505089