【LeetCode】#166分数到小数(Fraction to Recurring Decimal)

【LeetCode】#166分数到小数(Fraction to Recurring Decimal)

题目描述

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

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)”

Description

Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.
If the fractional part is repeating, enclose the repeating part in parentheses.

Example

Example 1:

Input: numerator = 1, denominator = 2
Output: “0.5”

Example 2:

Input: numerator = 2, denominator = 1
Output: “2”

Example 3:

Input: numerator = 2, denominator = 3
Output: “0.(6)”

解法

class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        HashMap map = new HashMap<>();
        List number = new ArrayList<>();
        int index = 0;
        int beginIndex = -1;
        StringBuilder sb = new StringBuilder();
        if(denominator==0)
            return "";
        long num = numerator;
        long denum = denominator;
        if(num<0 && denum>0 || (num>0 && denum<0)){
            sb.append("-");
        }
        num = Math.abs(num);
        denum = Math.abs(denum);
        long val = num / denum;
        sb.append(String.valueOf(val));
        num = (num%denum)*10;
        while(num!=0){
            if(map.containsKey(num)){
                beginIndex = map.get(num);
                break;
            }else{
                map.put(num, index++);
                val = num / denum;
                num = (num%denum)*10;
                number.add(val);
            }
        }
        for(int i=0; i