C++ 高精度加法

#include 
#include 
#include 

using namespace std;

vector add(vector &A, vector &B)
{
    vector C;
    
    int t = 0;
    for ( int i = 0, la = A.size(), lb = B.size(); i < la || i < lb; i++ )
    {
        if ( i < la ) t += A[i];
        if ( i < lb ) t += B[i];
        C.push_back(t % 10);
        t /= 10;
    }
    if ( t ) C.push_back(1);
    return C;
}

int main()
{
    string a, b;
    vector A, B;
    
    cin >> a >> b;  // a = "123456"
    for ( int i = a.size() - 1; i >= 0; i-- ) A.push_back(a[i] - '0');  // A = [6, 5, 4, 3, 2, 1]
    for ( int i = b.size() - 1; i >= 0; i-- ) B.push_back(b[i] - '0');
    
    vector C = add(A, B);
    
    for ( int i = C.size() - 1; i >= 0; i-- ) cout << C[i];
    cout << endl;
    
    return 0;
}