模板：大整数除法

 1 string sub(string s1,string s2)
 2 {
 3     int flag = 0;
 4     if(s1.length()<s2.length() || (s1.length()==s2.length() && s1 < s2))
 5     {
 6         flag = 1;
 7         string temp=s1;
 8         s1=s2;
 9         s2=temp;
10     }
11 
12 
13     int i,j;
14     for(i=s1.length()-1,j=s2.length()-1;i>=0;i--,j--)
15     {
16         s1[i]=char(s1[i]-(j>=0?s2[j]-'0':0));   //注意细节
17         if(s1[i]-'0'<0)
18         {
19             s1[i]=char(s1[i] + 10);
20             s1[i-1]--;
21         }
22     }
23 
24     for(i = 0; i < s1.length(); i++)
25     {
26         if(s1[i] != '0') break;
27     }
28     if(i == s1.length()) i = s1.length()-1;
29     s1 = s1.substr(i);
30 
31     if(flag) s1 = "-" + s1;
32 
33     return s1;
34 }
35 string sum(string s1,string s2)
36 {
37     if(s1.length()<s2.length())
38     {
39         string temp=s1;
40         s1=s2;
41         s2=temp;
42     }
43     int i,j;
44     for(i=s1.length()-1,j=s2.length()-1;i>=0;i--,j--)
45     {
46         s1[i]=char(s1[i]+(j>=0?s2[j]-'0':0));   //注意细节
47         if(s1[i]-'0'>=10)
48         {
49             s1[i]=char((s1[i]-'0')%10+'0');
50             if(i) s1[i-1]++;
51             else s1='1'+s1;
52         }
53     }
54     return s1;
55 }
56 
57 string div(string s1,string s2)
58 {
59     string res = "0";
60     if(s1.length()<s2.length() || (s1.length()==s2.length() && s1 < s2))
61     {
62         return "0";
63     }
64 
65     int i;
66     int sub_length = s1.length() - s2.length();
67     for(i = sub_length; i >= 0; i--)
68     {
69         string s3(i,'0');
70         string s4 = s2 + s3;
71         
72         do
73         {
74             string temp = sub(s1,s4);
75             if(temp[0] == '-') break;
76             else
77             {
78                 s1 = temp;
79                 res = sum(res,("1" + s3));
80             }
81         }while(1);
82     }
83     return res;
84 }