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();
     }
 }