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大数字减法

Posted on 2015-09-16 09:39  糖醋里脊er  阅读(190)  评论(0)    收藏  举报
.大数求差，给两个字符串（1-100位），求他们的差，如果是负数，则输出负数。
如：“1111111111”，“1234678899879"输出:-1233567788768
 
 
 1 package com.huawei;
 2 
 3 import java.math.BigDecimal;
 4 
 5 public class BigDic
 6 {
 7 
 8     public static void main(String[] args)
 9     {
10         System.out.println(4-8);
11         System.out.println(sub("23456789234567891234567891111","1234567891234567891234567891111234567891234567891111234567891234567891111"));
12         System.out.println(sub2("23456789234567891234567891111","1234567891234567891234567891111234567891234567891111234567891234567891111"));
13     }
14     private static String sub2(String first, String second)
15     {
16         String res = "";
17         char[] a = new StringBuilder(first).reverse().toString().toCharArray();
18         char[] b = new StringBuilder(second).reverse().toString().toCharArray();
19         int firestLength = first.length();
20         int secondLength = second.length();
21         char sign = '+';
22         boolean jiewei = false;
23         int maxLength  = firestLength > secondLength ? firestLength :secondLength;
24         
25         if(firestLength < secondLength)
26         {
27             sign='-';
28         }
29         else if(firestLength == secondLength)
30         {
31             sign = a[a.length-1] > b[b.length-1] ? '+':'-';
32         }
33         
34         //    System.out.println("sign="+sign);
35         for(int i = 0;i < maxLength;i++)
36         {
37             
38             int f1 = i < firestLength ? a[i] - '0' : 0;
39             int s1 = i < secondLength ? b[i] - '0' : 0;
40             int temp = 0;
41             if(firestLength < secondLength)
42             {
43                   s1 = jiewei == true ? s1 - 1 : s1;
44                   temp = s1 - f1;
45                   jiewei = s1 - f1 < 0 ? true : false;
46                   temp = jiewei==true ? temp+10:temp;
47                   
48             }
49             else
50             {
51                   f1 = jiewei == true ? f1 - 1 : 1;
52                  temp = f1 - s1;
53                  jiewei = f1 - s1 < 0 ? true : false;
54                  temp = jiewei==true ? temp+10:temp;
55             }
56             
57             res = temp + res;
58         }
59         res = sign =='+' ? res : '-'+res;
60         return res;
61     }
62     public static String sub(String first,String second)
63     {
64         BigDecimal a = new BigDecimal(first);
65         BigDecimal b = new BigDecimal(second);
66         return a.subtract(b).toString();
67     }
68 }