高精度模板（vector版）

加法

#include<iostream>
#include<vector>
#include<cstring>

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;
    cin >> a >> b;
    vector<int> 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');

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

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

减法

#include<iostream>
#include<cstring>
#include<vector>

using namespace std;

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

    for (int i = 0, t = 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[C.size() - 1] == 0) C.pop_back();
    return C;
}

int main() {
    string a, b;
    cin >> a >> b;
    bool flag = false;
    if (a.size() < b.size()) swap(a, b);
    else if (a.size() == b.size() && a < b) swap(a, b);
    else flag = true;

    vector<int> 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');

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

    if (flag) for (int i = C.size() - 1; i >= 0; i -- ) cout << C[i];
    else {
        cout << "-";
        for (int i = C.size() - 1; i >= 0; i -- ) cout << C[i];
    }
    return 0;
}

乘法

#include<iostream>
#include<cstring>
#include<vector>

using namespace std;

vector<int> mul(vector<int> &A, int b) {
    vector<int> C;
    for (int i = 0, t = 0; i < A.size() || t; i ++ ){
        if (i < A.size()) t += A[i] * b;
        C.push_back(t % 10);
        t /= 10;
    }
    while (C.size() > 1 && C[C.size() - 1] == 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');

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

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

    return 0;
}

除法

#include<iostream>
#include<cstring>
#include<vector>
#include<algorithm>

using namespace std;

vector<int> div(vector<int> &A, int b, int &r) {
    vector<int> C;
    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 = 0;
    vector<int> C = div(A, b, r);

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

test