166. Fraction to Recurring Decimal

题目：

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)".

链接： http://leetcode.com/problems/fraction-to-recurring-decimal/

题解：

这道题基本就是Divide Two Integers + 处理循环小数。一刷的时候果断放弃了，因为不想处理恶心的边界条件，不在一开始把int转为long的话后面会很难写。现在又看了一遍大家的答案，发现绝大多数是先把int转为long，我也就放心了。实在不行咱可以用Python写这个。

Java:

Time Complexity - O(n)， Space Complexity - O(n)

public class Solution {
public String fractionToDecimal(int numerator, int denominator) {
if (numerator == 0) return "0";
if (denominator == 0) throw new ArithmeticException();
boolean sameSign = (numerator > 0) ^ (denominator < 0);
long dividend = Math.abs((long)numerator);
long divisor = Math.abs((long)denominator);

String intPart = String.valueOf(dividend / divisor);
intPart = sameSign ? intPart : "-" + intPart;
long remainder = dividend % divisor;
if (remainder == 0) return intPart;

Map<Long, Integer> map = new HashMap<>();
StringBuilder decimalPart = new StringBuilder();

while (remainder != 0) {
map.put(remainder, decimalPart.length());
remainder *= 10;
decimalPart.append(remainder / divisor);
remainder = remainder % divisor;
if (map.containsKey(remainder)) {
decimalPart.insert(map.get(remainder), "(");
decimalPart.append(')');
break;
}
}

return intPart + "." + decimalPart.toString();
}
}

Python:

Time Complexity - O(n)， Space Complexity - O(n)

Test Cases:

(1, 3)

(1, 5)

(1, 6)

(1, 90)

(1, 99)

(22, 7)

(-50, 8)

(0, -5)

(-1, -2147483648)

(-2147483648, 1)

Reference：
https://leetcode.com/discuss/18731/accepted-cpp-solution-with-explainations https://leetcode.com/discuss/18769/there-good-deal-with-extreme-edge-case-without-converting-long https://leetcode.com/discuss/18989/online-judge-pass-java-version https://leetcode.com/discuss/20515/my-java-solution https://leetcode.com/discuss/22652/do-not-use-python-as-cpp-heres-a-short-version-python-code https://leetcode.com/discuss/23079/my-clean-java-solution https://leetcode.com/discuss/31521/short-java-solution https://leetcode.com/discuss/42159/0ms-c-solution-with-detailed-explanations https://leetcode.com/discuss/50512/accepted-clean-java-solution http://gqqnbig.me/?p=160 http://blog.csdn.net/hanshileiai/article/details/8861376 http://segmentfault.com/q/1010000003958185 https://leetcode.com/discuss/8886/my-simple-solution http://blog.csdn.net/ljiabin/article/details/42025037