高精度模板

赌一手今年 CSP 必考高精。

加法：

#include <bits/stdc++.h>
using namespace std;

string a, b;

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 % 10);
        t /= 10;
    }
    if (t) C.push_back(t);
    return C;
}

void output(vector<int> C) {
    for (int i = C.size() - 1; i >= 0; i--) cout << C[i];
}

int main() {
    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');
    vector<int> C = add(A, B);
    output(C);
}

减法、

#include <bits/stdc++.h>
using namespace std;

string a, b;

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] - 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;
}

void output(vector<int> C) {
    for (int i = C.size() - 1; i >= 0; i--) cout << C[i];
}

int main() {
    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');
    vector<int> C = add(A, B);
    output(C);
}

乘法（高精*低精）

#include <bits/stdc++.h>
using namespace std;

string a;
int b;

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

void output(vector<int> C) {
    for (int i = C.size() - 1; i >= 0; i--) cout << C[i];
}

int main() {
    vector<int> A;
    cin >> a >> b;
    for (int i = a.size() - 1; i >= 0; i--) A.push_back(a[i] - '0');
    output(mul(A, b));
}

除法（高精/低精）

#include <bits/stdc++.h>
using namespace std;

string a;
int b, r;

vector<int> div(vector<int> A, int b) {
    vector<int> C;
    for (int i = 0; i < A.size(); 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;
}

void output(vector<int> C) {
    for (int i = C.size() - 1; i >= 0; i--) cout << C[i];
    puts("");
    cout << r << endl;
}

int main() {
    vector<int> A;
    cin >> a >> b;
    for (int i = 0; i < a.size(); i++) A.push_back(a[i] - '0');
    output(div(A, b));
}