Leetcode 166.分数到小数

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)"

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

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