【模板小程序】大数相加（十进制）,包含合法性检查

 1 //大数相加（十进制）,用string处理
 2 #include <iostream>
 3 #include <string>
 4 #include <algorithm>
 5 
 6 using namespace std;
 7 
 8 //输入数据合法性检查,数字必须在0-9范围内
 9 bool IsVaild(const string& num1,const string& num2)
10 {
11     for(auto val:num1)
12     {
13         if(!(val>=‘0‘ && val-‘0‘<=‘9‘))
14             return false;
15     }
16     for(auto val:num2)
17     {
18         if(!(val>=‘0‘ && val<=‘9‘))
19             return false;
20     }
21     return true;
22 }
23 
24 string greatNumberAdd(string num1,string num2)
25 {
26     const size_t len1=num1.length();
27     const size_t len2=num2.length();
28     const size_t n=len1>len2 ? len1 :len2;
29     reverse(num1.begin(),num1.end());
30     reverse(num2.begin(),num2.end());
31 
32     string result;
33     int carry=0;
34     for(size_t i=0;i<n;++i)
35     {
36         const int num1i = i<len1 ? num1[i]-‘0‘ :0;
37         const int num2i = i<len2 ? num2[i]-‘0‘ :0;
38         const int val   = (num1i+num2i+carry)%10;
39         carry=(num1i+num2i+carry)/10;
40         result.insert(result.begin(),val+‘0‘);
41     }
42     if(1==carry)//若最前面有进位，则插入‘1‘
43         result.insert(result.begin(),‘1‘);
44 
45     return result;
46 }
47 
48 int main()
49 {
50     string num1,num2;
51     while(cin>>num1>>num2)
52     {
53         if(IsVaild(num1,num2))
54             cout<<greatNumberAdd(num1,num2)<<endl;
55         else
56             cout<<"输入数据不合法"<<endl;
57     }
58     return 0;
59 }