大数加法

 1 #include <iostream>
 2 
 3 using namespace std;
 4 
 5 string add(string str1, string str2)//大数加法
 6 {
 7     string str;
 8     int len1 = str1.length();
 9     int len2 = str2.length();
10     if(len1 < len2)
11     {
12         for(int i = 1; i <= len2 - len1; i++)
13         {
14             str1 = ‘0‘ + str1;
15         }
16     }
17     else {
18         for(int i = 1; i <= len1 - len2; i++)
19         {
20             str2 = "0" + str2;
21         }
22     }
23     len1 = str1.length();
24     int cmp = 0;
25     int ans;
26     for(int i = len1 - 1; i >= 0; i--)
27     {
28         ans = str1[i] - ‘0‘ + str2[i] - ‘0‘ + cmp;
29         cmp = ans/10;
30         ans %= 10;
31         str = char(ans + ‘0‘) + str;
32     }
33     return str;
34 }
35 
36 int main()
37 {
38     string a, b;
39     while(cin >> a >> b)
40     {
41         cout << add(a,b) << endl;
42     }
43     return 0;
44 }