Java实现 LeetCode 166 分数到小数

166. 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，以字符串形式返回小数。

如果小数部分为循环小数，则将循环的部分括在括号内。

示例 1:

输入: numerator = 1, denominator = 2
输出: “0.5”
示例 2:

输入: numerator = 2, denominator = 1
输出: “2”
示例 3:

输入: numerator = 2, denominator = 3
输出: “0.(6)”

class Solution {
       public String fractionToDecimal(int numerator, int denominator) {
        if (numerator == 0 || denominator == 0) return "0";
        int sign = 1;
        if (numerator > 0 && denominator < 0) sign = -1;
        long big = (long) numerator / (long) denominator;
        long small = numerator % denominator;
        StringBuilder result = new StringBuilder(String.valueOf(big));
        if (sign == -1) result.insert(0, "-");
        if (small != 0) {
            result.append(".");
            StringBuilder smallStr = new StringBuilder();
            Map<String, Integer> smallIndexs = new HashMap<String, Integer>();
            while (small != 0) {
                small *= 10;
                big = small / denominator;
                small = small % denominator;
                String str = small + "_" + big;
                if (smallIndexs.containsKey(str)) {
                    smallStr.append(")");
                    smallStr.insert(smallIndexs.get(str), "(");
                    break;
                } else {
                    smallIndexs.put(str, smallStr.length());
                    smallStr.append(Math.abs(big));
                }
            }
            result.append(smallStr);
        }
        return result.toString();
    }
}