不圧位代码

#include <iostream>
#include <vector>

using namespace std;

vector<int> add(vector<int> &A,vector<int> &B)
{
    if(A.size()<B.size()) return add(B,A);  //如果B位数多于A则反一下计算

    vector<int> C;
    int t=0;
    for(int i=0;i<A.size();i++)
    {
        t+=A[i];
        if(i<B.size()) t+=B[i];
        C.push_back(t%10);
        t/=10;
    }
    if(t) C.push_back(t); //最后可能还有一位进位
    return C;
}


int main(){
    string a,b;
    vector<int> A,B;
    cin >> a >> b ;

    for(int i=a.size()-1;i>=0;i--) A.push_back(a[i]-'0');
    for(int i=b.size()-1;i>=0;i--) B.push_back(b[i]-'0');

     auto C=add(A,B);

    for(int i=C.size()-1;i>=0;i--) cout<<C[i];
    cout<<endl;

    return 0;
}

压9位的代码
上面的代码中，数组里每一个数存0~9，压8位就是每个数存0~99999999。这样数组长度会缩小到八分之一

#include <iostream>
#include <vector>
using namespace std;
const int base = 1000000000;

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

int main()
{
    string a, b;
    vector<int> A, B;
    cin >> a >> b;

    for (int i = a.size() - 1, s = 0, j = 0, t = 1; i >= 0; i -- )
    {
        s += (a[i] - '0') * t;
        j ++, t *= 10;
        if (j == 9 || i == 0)
        {
            A.push_back(s);
            s = j = 0;
            t = 1;
        }
    }
    for (int i = b.size() - 1, s = 0, j = 0, t = 1; i >= 0; i -- )
    {
        s += (b[i] - '0') * t;
        j ++, t *= 10;
        if (j == 9 || i == 0)
        {
            B.push_back(s);
            s = j = 0;
            t = 1;
        }
    }

    auto C = add(A, B);
    cout << C.back();
    for (int i = C.size() - 2; i >= 0; i -- ) printf("%09d", C[i]);
    cout << endl;
    return 0;
}