166. 分數到小數

給定兩個整數，分別表示分數的分子 numerator 和分母 denominator，以字符串形式返回小數。

如果小數部分爲循環小數，則將循環的部分括在括號內。

示例 1:

輸入: numerator = 1, denominator = 2
輸出: "0.5"

示例 2:

輸入: numerator = 2, denominator = 1
輸出: "2"

示例 3:

輸入: numerator = 2, denominator = 3
輸出: "0.(6)"

在真實的面試中遇到過這道題？

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Code:

這題真是越來越噁心了啊

class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        String res = "";
        if (numerator<0 && denominator>0 || numerator>0&&denominator<0) {
            res+='-';
        }
        long num = Math.abs((long) numerator);
        long dev = Math.abs((long) denominator);

        long result = num/dev;
        res+=Long.toString(result);
        if (result*dev==num){
            return res;
        }
        res+='.';

        num -= result*dev;
        num*=10;
        HashMap<Long, Integer> map = new HashMap<>();
        StringBuilder sb = new StringBuilder();
        int idx = 0;
        map.put(num,idx++);
        while (true){
            result = num / dev;
            sb.append(result);
            num-=result*dev;
            if (num==0){
                break;
            }
            num*=10;
            if(map.containsKey(num)){
                sb.append(')');
                sb.insert((int)map.get(num),'(');
                break;
            } else {
                map.put(num, idx++);
            }
            
        }
        return res+sb.toString();
    }
}