166. 分数到小数

为保证权益，题目请参考 166. 分数到小数(From LeetCode).

解决方案1

CPP

//
// Created by lenovo on 2020-09-30.
//

#include <iostream>
#include <string>
#include <vector>
#include <unordered_set>
#include <unordered_map>

using namespace std;

class Solution {
public:
    string fractionToDecimal(long long  numerator, long long denominator) {
        int sign = 1;
        if ((numerator < 0 && denominator > 0) || (numerator > 0 && denominator < 0)) {
            sign = -1;
            numerator = numerator > 0 ? numerator : -numerator;
            denominator = denominator > 0 ? denominator : -denominator;
        }

        string ans = "";
        long long a = 0;
        long long b = 0;

        a = numerator / denominator;
        b = numerator % denominator;
        ans += to_string(a);
        ans += b == 0 ? "" : ".";

        unordered_map<int, int> aHistory;
        aHistory.emplace(numerator, -1);

        int position = to_string(a).length() + 1;

        while (b) {
            b = b * 10;
            if (aHistory.find(b) != aHistory.end()) {
                ans.insert(aHistory[b], "(");
                ans += ")";
                break;
            }
            aHistory.emplace(b, position);
            position += 1;
            a = b / denominator;
            b = b % denominator;
            ans += to_string(a);
        }
        ans = (sign == 1 ? "" : "-") + ans;
        return ans;
    }
};

void runTest() {
    Solution so;
    cout << so.fractionToDecimal(1, 3);
}

int main() {
    runTest();
    return 0;
}

Python

# 166. 分数到小数
# https://leetcode-cn.com/problems/fraction-to-recurring-decimal/

################################################################################


class Solution:
    def fractionToDecimal(self, numerator: int, denominator: int) -> str:

        isNegative = False
        if (numerator < 0 and denominator > 0) or (numerator > 0 and denominator < 0):
            isNegative = True
            numerator = -numerator if numerator < 0 else numerator
            denominator = -denominator if denominator < 0 else denominator

        intergerNum, left = divmod(numerator, denominator)

        if left == 0:
            if intergerNum == 0:
                return str(intergerNum)
            else:
                if isNegative:
                    return str(-intergerNum)
                else:
                    return str(intergerNum)

        a = left
        b = denominator
        d = dict()
        decimals = []
        targetIndex = -1
        for i in range(10005):
            if a == 0:
                break
            a = a * 10
            if a in d:
                targetIndex = d[a]
                break
            else:
                d[a] = i
                c, e = divmod(a, b)
                decimals.append(str(c))
                a = e

        if targetIndex != -1:
            decimals.insert(targetIndex, "(")
            decimals.append(")")

        if isNegative:
            return "-" + str(intergerNum) + "." + "".join(decimals)
        else:
            return str(intergerNum) + "." + "".join(decimals)


################################################################################

if __name__ == "__main__":
    solution = Solution()
    print(solution.fractionToDecimal(27, 12))