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)"

 1 import java.util.ArrayList;
 2 import java.util.HashMap;
 3 import java.util.List;
 4 
 5 public class Solution {
 6     public static String fractionToDecimal(int numerator, int denominator) {
 7         HashMap<Long,Integer> maps = new HashMap<>();//store divid number
 8         List<Long> number = new ArrayList<>();
 9         int index = 0; int beginIndex = -1;
10         StringBuilder builder = new StringBuilder();
11         if(denominator==0) return "";
12         long num = numerator;
13         long denum = denominator;
14         if((num<0 && denum>0) || (num>0 && denum<0))
15             builder.append('-');
16         num = Math.abs(num);
17         denum = Math.abs(denum);
18         long val = num/denum;
19         builder.append(String.valueOf(val));
20         num = (num%denum)*10;
21         while(num!=0){
22             if(maps.containsKey(num)){//开始重复
23                 beginIndex = maps.get(num);
24                 break;
25             }else{
26                 maps.put(num, index++);
27                 val = num/denum;
28                 num = (num%denum)*10;
29                 number.add(val);
30             }
31         }
32         for(int i = 0;i<index;i++){
33             if(i==0)
34                 builder.append('.');
35             if(i==beginIndex){
36                 builder.append('(');
37             }
38             builder.append(number.get(i));
39         }
40         if(beginIndex!=-1)
41             builder.append(')');
42         return builder.toString();
43     }
44 }