2021-10-20：分数到小数。给定两个整数，分别表示分数的分子numerator和分母denominator，以字符串形式返

package main

import "fmt"

func main() {
    a := 3
    b := 11
    ret := fractionToDecimal(a, b)
    fmt.Println(ret)
    fmt.Println(3.0 / 11.0)
}
func fractionToDecimal(numerator, denominator int) string {
    if numerator == 0 {
        return "0"
    }
    //StringBuilder res = new StringBuilder();
    res := make([]byte, 0)
    // "+" or "-"
    //res.append(((numerator > 0) ^ (denominator > 0)) ? "-" : "");
    if (numerator > 0 && !(denominator > 0)) || (!(numerator > 0) && denominator > 0) {
        res = append(res, []byte("-")...)
    } else {
        res = append(res, []byte("")...)
    }
    num := Abs(numerator)
    den := Abs(denominator)
    // integral part
    //res.append(num / den);
    res = append(res, []byte(fmt.Sprint(num/den))...)
    num %= den
    if num == 0 {
        return string(res)
    }
    // fractional part
    res = append(res, []byte(".")...)
    map0 := make(map[int]int)
    map0[num] = len(res)
    for num != 0 {
        num *= 10
        res = append(res, []byte(fmt.Sprint(num/den))...)
        num %= den
        if _, ok := map0[(num)]; ok {
            index := map0[num]
            //res.insert(index, "(")
            rescopy := make([]byte, 0)
            rescopy = append(rescopy, res[0:index]...)
            rescopy = append(rescopy, []byte("(")...)
            rescopy = append(rescopy, res[index:]...)
            res = rescopy
            res = append(res, []byte(")")...)
            break
        } else {
            map0[num] = len(res)
        }
    }
    return string(res)
}

func Abs(a int) int {
    if a < 0 {
        return -a
    } else {
        return a
    }
}