LeetCode 166：Fraction to Recurring Decimal

被打的小怪兽

于 2019-09-18 11:14:01 发布

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本文介绍了一种将任意两个整数表示的分数转换为字符串格式的小数的方法，特别关注于如何处理循环小数部分，并通过C++代码示例详细展示了算法的实现过程。

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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)”

C++
string fractionToDecimal(int numerator, int denominator) {
        int s1 = numerator > 0 ? 1 : -1;
        int s2 = denominator > 0 ? 1 : -1;
        long long num = abs((long long)numerator);
        long long den = abs((long long)denominator);
        long long out = num/den;
        long long rem = num%den;
        string res = to_string(out);
        if(s1*s2 == -1&&(out > 0||rem > 0))res = '-' + res;
        if(rem == 0)return res;
        res += '.';
        unordered_map<long long,int> m;
        int pos = 0;
        string s = "";
        while(rem != 0)
        {
            if(m.find(rem) != m.end())
            {
                s.insert(m[rem],"(");
                s += ")";
                return res + s;
            }
            m[rem] = pos;
            pos++;
            s += to_string((rem*10)/den);
            rem = (rem*10)%den;
        }
        return res + s;
    }