【刷题-LeetCode】166 Fraction to Recurring Decimal

166. Fraction to 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.

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)"

解 当余数重复出现时，意味着循环节出现了。因此需要用一个字典pos记录每个余数出现的位置，重复出现的余数对应的两个位置之间的即为循环节

Note: 运行时发现数字会出现溢出的问题，代码中的类型改成了long long int

class Solution {
public:
    string fractionToDecimal(long long int numerator, int denominator) {
        string res;
        if(numerator < 0 && denominator > 0){
            numerator *= -1;
            res += "-";
        }else if(numerator > 0 && denominator < 0){
            denominator *= -1;
            res += "-";
        }
        res += to_string(divmod(numerator, denominator));
        if(numerator == 0)return res;
        res += ".";
        map<int, int>mp;
        mp[numerator] = res.size();
        while(numerator){
            numerator *= 10;
            int tmp = divmod(numerator, denominator);
            res += to_string(tmp);
            if(mp.find(numerator) != mp.end()){
                res.insert(mp[numerator], "(");
                res += ")";
                break;
            }
            mp[numerator] = res.size();
        }
        return res;

    }
    long long int divmod(long long int &n1, int &n2){
        long long int res = n1 / n2;
        n1 -= res * n2;
        return res;
    }
};