C++ large integer summation algorithm (complete example)

What is a large integer?

We know that in compiling software, the representation of integers has a range, which cannot satisfy the summation operation of huge numbers, that is, large integers. So we split and store each number in an array for addition and subtraction.

Not much to say, directly on the code:

#include <iostream>
using namespace std;
const int MaxSize=100;  
template <class DataType>           //模板类
class SeqList
{
 public:  
     SeqList( ) ;                                 //构造函数
     SeqList(DataType a[ ], int n);       
     ~SeqList( ) { }; 
	 void PrintList();                              //析构函数
	 friend SeqList<int> Add(SeqList <int> A,SeqList <int> B);  
     DataType data[MaxSize]; 
     int length;
};
template <class DataType>  
SeqList<DataType> ::SeqList( )
{  
    length = 0; 
}
template <class DataType>  
SeqList<DataType> ::SeqList(DataType a[ ], int n)
{  
       if (n > MaxSize) throw "参数非法";
       for (int i = 0; i < n; i++)  
             data[i] = a[i];
       length = n; 
 }
template <class DataType>
void SeqList<DataType> ::  PrintList()
{
	for(int i=0; i<length; i++)
	cout<<data[i];
 } 
SeqList<int> Add(SeqList <int> A,SeqList <int> B)
{
	SeqList<int> C;
	int flag=0;int i=0;
	int n=A.length;int m=B.length;
	while (i<n && i<m)
	{
		C.data[i]=(A.data[i]+B.data[i]+flag)%10;
		flag=(A.data[i]+B.data[i]+flag)/10;
		i++;
	}
	for(; i<n; i++)
	{
		C.data[i]=(A.data[i]+flag)%10;
		flag=(A.data[i]+flag)/10;
	}
	for(; i<m; i++)
	{
		C.data[i]=(B.data[i]+flag)%10;
		flag=(B.data[i]+flag)/10;
	}
	C.length=max(m,n)+flag;
	if(flag==1) C.data[C.length-1]=1;
	return C;
}
int main()
{
	int a[5]={1,2,3,4,5},b[5]={1,2,3,4,5};
	SeqList <int>A(a,5);
	cout<<"大整数A：";A.PrintList();cout<<endl; 
	SeqList <int>B(b,5);
	cout<<"大整数B：";B.PrintList();cout<<endl; 
	SeqList <int>C;
	C=Add(A,B);
	cout<<"A+B=";C.PrintList();cout<<endl; 
	return 0;
}