Leetcode: Fraction to Recurring Decimal, leetcoderecurring

Leetcode: Fraction to Recurring Decimal, leetcoderecurring

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. Use a map to record the divisor changes in the process of dividing n by d, and the location of the corresponding operator in the returned result string when the divisor is n (.

2. When the negative number is positive, it will cross the border. The following example 2 ^ 31 = 2 147 483 648, int indicates the range (-2147483648 ~ 2147483647), so use 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;}};