高精度(高精加，高精减，高精乘，高精除)

高精加

#include<iostream>
#include<vector>
#include<string>
using namespace std;

vector<int> add(vector<int> &A, vector<int> &B)
{
    vector<int> C;

    int t = 0;
    for(int i = 0; i < A.size() || i < B.size(); i++)
    {
        if(i < A.size()) t += A[i];
        if(i < B.size()) t += B[i];
        C.push_back(t % 10);
        t /= 10;
    }
    if(t) C.push_back(1);
    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];
    system("pause");
    return 0;
}

高精度减

#include<iostream>
#include<vector>
#include<string>
using namespace std;

bool cmp(vector<int> &A, vector<int> &B)
{
    if(A.size() != B.size()) return A.size() > B.size();
    for(int i = A.size()-1; i >= 0; i--)
        if(A[i] != B[i])
            return A[i] > B[i];
    return true;
}

vector<int> sub(vector<int> &A, vector<int> &B)
{
    vector<int> C;

    int t = 0;
    for(int i = 0; i < A.size(); i++)
    {
        t = A[i]-t;
        if(i < B.size()) t -= B[i];
        C.push_back((t+10)%10);
        if(t < 0) t = 1;
        else t = 0;
    }
    while(C.size() > 1 && C.back() == 0) C.pop_back();
    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');
    
    if(cmp(A, B))  //如果A >= B
    {
        auto C = sub(A, B);
        for(int i = C.size()-1; i >= 0; i--) cout << C[i];
    }
    else
    {
        auto C = sub(B, A);

        printf("-");
        for(int i = C.size()-1; i >= 0; i--) cout << C[i];
    }
    
    system("pause");
    return 0;
}

高精乘

#include<iostream>
#include<string>
#include<vector>
using namespace std;

vector<int> mul(vector<int> A, int b)
{
    vector<int> C;

    int t = 0;
    for(int i = 0; i < A.size() || t; i++)  //这样最高位可以直接添加
    {
        if(i < A.size()) t += A[i]*b;
        C.push_back(t % 10);
        t /= 10;
    }
    return C;
}

int main()
{
    string a;
    int b;

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

    auto C = mul(A, b);

    while(C.size() > 1 && C.back() == 0) C.pop_back();
    for(int i = C.size()-1; i >= 0; i--) cout << C[i];
    system("pause");
    return 0;
}

高精除法

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
using namespace std;

vector<int> div(vector<int> A, int b, int &r)
{
    vector<int> C;
    
    r = 0;
    for(int i = A.size()-1; i >= 0; i--)
    {
        r = r*10+A[i];
        C.push_back(r/b);
        r %= b;
    }
    
    reverse(C.begin(), C.end());
    while(C.size() > 1 && C.back() == 0) C.pop_back();
    return C;
}

int main()
{
    string a;
    int b;

    cin >> a >> b;
    vector<int> A;
    for(int i = a.size()-1; i >= 0; i--) A.push_back(a[i]-'0');
    
    int r; //用来储存余数
    auto C = div(A, b, r);

    for(int i = C.size()-1; i >= 0; i--) cout << C[i];
    cout << endl << r << endl;
    system("pause");
    return 0;
}