模板：浮点数加法

 1 #include <cstdio>
 2 #include <string>
 3 
 4 string sum(string s1,string s2)
 5 {
 6     if(s1.length()<s2.length())
 7     {
 8         string temp=s1;
 9         s1=s2;
10         s2=temp;
11     }
12     int i,j;
13     for(i=s1.length()-1,j=s2.length()-1;i>=0;i--,j--)
14     {
15         s1[i]=char(s1[i]+(j>=0?s2[j]-'0':0));   //注意细节
16         if(s1[i]-'0'>=10)
17         {
18             s1[i]=char((s1[i]-'0')%10+'0');
19             if(i) s1[i-1]++;
20             else s1='1'+s1;
21         }
22     }
23     return s1;
24 }
25 
26 string real_sum(string s1,string s2)
27 {
28     string::size_type idx_s1_point = s1.find(".");
29     s1.erase(idx_s1_point,1);
30 
31     string::size_type idx_s2_point = s2.find(".");
32     s2.erase(idx_s2_point,1);
33 
34     string::size_type int_res_len = idx_s1_point>idx_s2_point?idx_s1_point:idx_s2_point;
35 
36     string::size_type dec_s1_len = s1.size() - idx_s1_point;
37     string::size_type dec_s2_len = s2.size() - idx_s2_point;
38 
39     
40 
41     string::size_type dec_res_len;
42     if(dec_s1_len < dec_s2_len)
43     {
44         s1 += string(dec_s2_len - dec_s1_len, '0');
45         dec_res_len = dec_s2_len;
46     }
47     else
48     {
49         s2 += string(dec_s1_len - dec_s2_len, '0');
50         dec_res_len = dec_s1_len;
51     }
52 
53     string res = sum(s1,s2);
54 
55     if(res.size() > int_res_len + dec_res_len)
56     {
57         ++int_res_len;
58     }
59 
60     string::size_type idx_res_tail = res.find_last_not_of("0");
61 
62     res = res.substr(0,idx_res_tail + 1);
63     res.insert(int_res_len,".");
64 
65     return res;
66 }