leetcode 166. Fraction to Recurring Decimal

166. Fraction to Recurring Decimal

https://www.cnblogs.com/grandyang/p/4238577.html

用一个哈希表判断余数是否重复，重复了就有无限循环小数，就可以停止加括号了

class Solution {
public:
    string fractionToDecimal(int numerator, int denominator) {
        int flag1 = numerator > 0 ? 1 : -1;
        int flag2 = denominator > 0 ? 1 : -1;
        long num1 = abs((long)numerator);
        long num2 = abs((long)denominator);
        long num = num1 / num2;
        long rem = num1 % num2;
        unordered_map<int,int> m;
        string res = to_string(num);
        if(flag1 * flag2 == -1 && (num != 0 || rem != 0))
            res = "-" + res;
        if(rem == 0)
            return res;
        res += ".";
        int index = res.size();
        while(rem){
            if(m.find(rem) != m.end()){
                res.insert(m[rem],"(");
                res += ")";
                return res;
            }
            m[rem] = index;
            num = rem*10 / num2;
            rem = rem*10 % num2;
            res += to_string(num);
            ++index;
        }
        return res;
    }
};

自己又写了一遍

class Solution {
public:
    string fractionToDecimal(int numerator, int denominator) {
        if(denominator == 0)
            return "";
        bool flag;
        if((numerator >= 0 && denominator > 0) || (numerator <= 0 && denominator < 0))
            flag = true;
        else
            flag = false;
        long num1 = abs((long)numerator);
        long num2 = abs((long)denominator);
        long num = num1/num2;
        long rem = num1%num2;
        string res;
        res += to_string(num);
        if(!flag)
            res = "-" + res;
        if(rem == 0)
            return res;
        res += ".";
        unordered_map<long,int> m;
        int index = res.size();
        while(rem != 0){
            if(m.find(rem) != m.end()){
                res.insert(m[rem],"(");
                res += ")";
                return res;
            }
            m[rem] = index;
            long tmp = rem*10/num2;
            rem = rem*10%num2;
            res += to_string(tmp);
            index++;
        }
        return res;
    }
};