• 转载自 wkh2008 。

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

namespace BIGINT {
using cpx = complex<double>;
const double PI = acos(-1);
vector<cpx>roots = {{0, 0}, {1, 0}};
void ensure_capacity(int min_capacity) {
    for (int len = roots.size(); len < min_capacity; len *= 2) {
        for (int i = len >> 1; i < len; i++) {
            roots.emplace_back(roots[i]);
            double angle = 2 * PI * (2 * i + 1 - len) / (len * 2);
            roots.emplace_back(cos(angle), sin(angle));
        }
    }
} void fft(vector<cpx> &z, bool inverse) {
    size_t n = z.size();
    assert((n & (n - 1)) == 0);
    ensure_capacity(n);

    for (size_t i = 1, j = 0; i < n; i++) {
        size_t bit = n >> 1;

        for (; j >= bit; bit >>= 1)
            j -= bit;

        j += bit;

        if (i < j)
            swap(z[i], z[j]);
    }

    for (size_t len = 1; len < n; len <<= 1) {
        for (size_t i = 0; i < n; i += len * 2) {
            for (size_t j = 0; j < len; j++) {
                cpx root = inverse ? conj(roots[j + len]) : roots[j + len];
                cpx u = z[i + j];
                cpx v = z[i + j + len] * root;
                z[i + j] = u + v;
                z[i + j + len] = u - v;
            }
        }
    }

    if (inverse)
        for (size_t i = 0; i < n; i++)
            z[i] /= n;
} vector<int>multiply_BI(const vector<int> &a, const vector<int> &b, int base) {
    size_t need = a.size() + b.size();
    size_t n = 1;

    while (n < need)
        n <<= 1;

    vector<cpx>p(n);

    for (size_t i = 0; i < n; i++) {
        p[i] = cpx(i < a.size() ? a[i] : 0, i < b.size() ? b[i] : 0);
    }

    fft(p, false);
    vector<cpx>ab(n);
    cpx r(0, -0.25);

    for (size_t i = 0; i < n; i++) {
        int j = (n - i) & (n - 1);
        ab[i] = (p[i] * p[i] - conj(p[j] * p[j])) * r;
    }

    fft(ab, true);
    vector<int>result(need);
    long long carry = 0;

    for (size_t i = 0; i < need; i++) {
        long long d = (long long)(ab[i].real() + 0.5) + carry;
        carry = d / base;
        result[i] = d % base;
    }

    return result;
} vector<int>multiply_mod(const vector<int> &a, const vector<int> &b, int m) {
    int need = a.size() + b.size() - 1;
    int n = 1;

    while (n < need)
        n <<= 1;

    vector<cpx>A(n);

    for (size_t i = 0; i < a.size(); i++) {
        int x = (a[i] % m + m) % m;
        A[i] = cpx(x & ((1 << 15) - 1), x >> 15);
    }

    fft(A, false);
    vector<cpx>B(n);

    for (size_t i = 0; i < b.size(); i++) {
        int x = (b[i] % m + m) % m;
        B[i] = cpx(x & ((1 << 15) - 1), x >> 15);
    }

    fft(B, false);
    vector<cpx>fa(n);
    vector<cpx>fb(n);

    for (int i = 0, j = 0; i < n; i++, j = n - i) {
        cpx a1 = (A[i] + conj(A[j])) * cpx(0.5, 0);
        cpx a2 = (A[i] - conj(A[j])) * cpx(0, -0.5);
        cpx b1 = (B[i] + conj(B[j])) * cpx(0.5, 0);
        cpx b2 = (B[i] - conj(B[j])) * cpx(0, -0.5);
        fa[i] = a1 * b1 + a2 * b2 * cpx(0, 1);
        fb[i] = a1 * b2 + a2 * b1;
    }

    fft(fa, true);
    fft(fb, true);
    vector<int>res(need);

    for (int i = 0; i < need; i++) {
        long long aa = (long long)(fa[i].real() + 0.5);
        long long bb = (long long)(fb[i].real() + 0.5);
        long long cc = (long long)(fa[i].imag() + 0.5);
        res[i] = (aa % m + (bb % m << 15) + (cc % m << 30)) % m;
    }

    return res;
} constexpr int digits(int base)noexcept {
    return base <= 1 ? 0 : 1 + digits(base / 10);
} constexpr int base = 1000'000'000;
constexpr int base_digits = digits(base);
constexpr int fft_base = 10'000;
constexpr int fft_base_digits = digits(fft_base);
struct BI {
    vector<int>z;
    int sign;
    BI(long long v = 0) {
        *this = v;
    } BI &operator=(long long v) {
        sign = v < 0 ? -1 : 1;
        v *= sign;
        z.clear();

        for (; v > 0; v = v / base)
            z.push_back((int)(v % base));

        return*this;
    } BI(const string &s) {
        read(s);
    } BI &operator+=(const BI &other) {
        if (sign == other.sign) {
            for (size_t i = 0, carry = 0; i < other.z.size() || carry; ++i) {
                if (i == z.size())
                    z.push_back(0);

                z[i] += carry + (i < other.z.size() ? other.z[i] : 0);
                carry = z[i] >= base;

                if (carry)
                    z[i] -= base;
            }
        } else if (other != 0) {
            *this -= -other;
        }

        return*this;
    } friend BI operator+(BI a, const BI &b) {
        a += b;
        return a;
    } BI &operator-=(const BI &other) {
        if (sign == other.sign) {
            if ((sign == 1 && *this >= other) || (sign == -1 && *this <= other)) {
                for (size_t i = 0, carry = 0; i < other.z.size() || carry; ++i) {
                    z[i] -= carry + (i < other.z.size() ? other.z[i] : 0);
                    carry = z[i] < 0;

                    if (carry)
                        z[i] += base;
                }

                trim();
            } else {
                *this = other - *this;
                this->sign = -this->sign;
            }
        } else {
            *this += -other;
        }

        return*this;
    } friend BI operator-(BI a, const BI &b) {
        a -= b;
        return a;
    } BI &operator*=(int v) {
        if (v < 0)
            sign = -sign, v = -v;

        for (size_t i = 0, carry = 0; i < z.size() || carry; ++i) {
            if (i == z.size())
                z.push_back(0);

            long long cur = (long long)z[i] * v + carry;
            carry = (int)(cur / base);
            z[i] = (int)(cur % base);
        }

        trim();
        return*this;
    } BI operator*(int v)const {
        return BI(*this) *= v;
    } friend pair<BI, BI>divmod(const BI &a1, const BI &b1) {
        int norm = base / (b1.z.back() + 1);
        BI a = a1.abs() * norm;
        BI b = b1.abs() * norm;
        BI q, r;
        q.z.resize(a.z.size());

        for (int i = (int)a.z.size() - 1; i >= 0; i--) {
            r *= base;
            r += a.z[i];
            int s1 = b.z.size() < r.z.size() ? r.z[b.z.size()] : 0;
            int s2 = b.z.size() - 1 < r.z.size() ? r.z[b.z.size() - 1] : 0;
            int d = (int)(((long long)s1 * base + s2) / b.z.back());
            r -= b * d;

            while (r < 0)
                r += b, --d;

            q.z[i] = d;
        }

        q.sign = a1.sign * b1.sign;
        r.sign = a1.sign;
        q.trim();
        r.trim();
        return{q, r / norm};
    } friend BI sqrt(const BI &a1) {
        BI a = a1;

        while (a.z.empty() || a.z.size() % 2 == 1)
            a.z.push_back(0);

        int n = a.z.size();
        int firstDigit = (int)::sqrt((double)a.z[n - 1] * base + a.z[n - 2]);
        int norm = base / (firstDigit + 1);
        a *= norm;
        a *= norm;

        while (a.z.empty() || a.z.size() % 2 == 1)
            a.z.push_back(0);

        BI r = (long long)a.z[n - 1] * base + a.z[n - 2];
        firstDigit = (int)::sqrt((double)a.z[n - 1] * base + a.z[n - 2]);
        int q = firstDigit;
        BI res;

        for (int j = n / 2 - 1; j >= 0; j--) {
            for (;; --q) {
                BI r1 = (r - (res * 2 * base + q) * q) * base * base + (j > 0 ? (long long)a.z[2 * j - 1] * base + a.z[2 * j -
                        2] : 0);

                if (r1 >= 0) {
                    r = r1;
                    break;
                }
            }

            res *= base;
            res += q;

            if (j > 0) {
                int d1 = res.z.size() + 2 < r.z.size() ? r.z[res.z.size() + 2] : 0;
                int d2 = res.z.size() + 1 < r.z.size() ? r.z[res.z.size() + 1] : 0;
                int d3 = res.z.size() < r.z.size() ? r.z[res.z.size()] : 0;
                q = (int)(((long long)d1 * base * base + (long long)d2 * base + d3) / (firstDigit * 2));
            }
        }

        res.trim();
        return res / norm;
    } BI operator/(const BI &v)const {
        return divmod(*this, v).first;
    } BI operator%(const BI &v)const {
        return divmod(*this, v).second;
    } BI &operator/=(int v) {
        if (v < 0)
            sign = -sign, v = -v;

        for (int i = (int)z.size() - 1, rem = 0; i >= 0; --i) {
            long long cur = z[i] + rem * (long long)base;
            z[i] = (int)(cur / v);
            rem = (int)(cur % v);
        }

        trim();
        return*this;
    } BI operator/(int v)const {
        return BI(*this) /= v;
    } int operator%(int v)const {
        if (v < 0)
            v = -v;

        int m = 0;

        for (int i = (int)z.size() - 1; i >= 0; --i)
            m = (int)((z[i] + m * (long long)base) % v);

        return m * sign;
    } BI &operator*=(const BI &v) {
        *this = *this * v;
        return*this;
    } BI &operator/=(const BI &v) {
        *this = *this / v;
        return*this;
    } BI &operator%=(const BI &v) {
        *this = *this % v;
        return*this;
    } bool operator<(const BI &v)const {
        if (sign != v.sign)
            return sign < v.sign;

        if (z.size() != v.z.size())
            return z.size() * sign < v.z.size() * v.sign;

        for (int i = (int)z.size() - 1; i >= 0; i--)
            if (z[i] != v.z[i])
                return z[i] * sign < v.z[i] * sign;

        return false;
    } bool operator>(const BI &v)const {
        return v < *this;
    } bool operator<=(const BI &v)const {
        return!(v < *this);
    } bool operator>=(const BI &v)const {
        return!(*this < v);
    } bool operator==(const BI &v)const {
        return sign == v.sign && z == v.z;
    } bool operator!=(const BI &v)const {
        return!(*this == v);
    } void trim() {
        while (!z.empty() && z.back() == 0)
            z.pop_back();

        if (z.empty())
            sign = 1;
    } bool isZero()const {
        return z.empty();
    } friend BI operator-(BI v) {
        if (!v.z.empty())
            v.sign = -v.sign;

        return v;
    } BI abs()const {
        return sign == 1 ? *this : -*this;
    } long long longValue()const {
        long long res = 0;

        for (int i = (int)z.size() - 1; i >= 0; i--)
            res = res * base + z[i];

        return res * sign;
    } friend BI gcd(const BI &a, const BI &b) {
        return b.isZero() ? a : gcd(b, a % b);
    } friend BI lcm(const BI &a, const BI &b) {
        return a / gcd(a, b) * b;
    } void read(const string &s) {
        sign = 1;
        z.clear();
        int pos = 0;

        while (pos < (int)s.size() && (s[pos] == '-' || s[pos] == '+')) {
            if (s[pos] == '-')
                sign = -sign;

            ++pos;
        }

        for (int i = (int)s.size() - 1; i >= pos; i -= base_digits) {
            int x = 0;

            for (int j = max(pos, i - base_digits + 1); j <= i; j++)
                x = x * 10 + s[j] - '0';

            z.push_back(x);
        }

        trim();
    } friend istream &operator>>(istream &stream, BI &v) {
        string s;
        stream >> s;
        v.read(s);
        return stream;
    } friend ostream &operator<<(ostream &stream, const BI &v) {
        if (v.sign == -1)
            stream << '-';

        stream << (v.z.empty() ? 0 : v.z.back());

        for (int i = (int)v.z.size() - 2; i >= 0; --i)
            stream << setw(base_digits) << setfill('0') << v.z[i];

        return stream;
    } static vector<int>convert_base(const vector<int> &a, int old_digits, int new_digits) {
        vector<long long>p(max(old_digits, new_digits) + 1);
        p[0] = 1;

        for (size_t i = 1; i < p.size(); i++)
            p[i] = p[i - 1] * 10;

        vector<int>res;
        long long cur = 0;
        int cur_digits = 0;

        for (int v : a) {
            cur += v * p[cur_digits];
            cur_digits += old_digits;

            while (cur_digits >= new_digits) {
                res.push_back(int(cur % p[new_digits]));
                cur /= p[new_digits];
                cur_digits -= new_digits;
            }
        }

        res.push_back((int)cur);

        while (!res.empty() && res.back() == 0)
            res.pop_back();

        return res;
    } BI operator*(const BI &v)const {
        if (min(z.size(), v.z.size()) < 150)
            return mul_simple(v);

        BI res;
        res.sign = sign * v.sign;
        res.z = multiply_BI(convert_base(z, base_digits, fft_base_digits), convert_base(v.z, base_digits,
                            fft_base_digits), fft_base);
        res.z = convert_base(res.z, fft_base_digits, base_digits);
        res.trim();
        return res;
    } BI mul_simple(const BI &v)const {
        BI res;
        res.sign = sign * v.sign;
        res.z.resize(z.size() + v.z.size());

        for (size_t i = 0; i < z.size(); ++i)
            if (z[i])
                for (size_t j = 0, carry = 0; j < v.z.size() || carry; ++j) {
                    long long cur = res.z[i + j] + (long long)z[i] * (j < v.z.size() ? v.z[j] : 0) + carry;
                    carry = (int)(cur / base);
                    res.z[i + j] = (int)(cur % base);
                }

        res.trim();
        return res;
    }
};
mt19937 rng(1);
BI random_BI(int n) {
    string s;

    for (int i = 0; i < n; i++) {
        s += uniform_int_distribution<int>('0', '9')(rng);
    }

    return BI(s);
}
}

signed main() {
    BIGINT::BI a, b;
    cin >> a >> b;
    cout << a / b << '\n';
    return 0;
}

使用指南

可视为 \(int\) ，但不可以用 \(memset\) ，位运算等函数，作为下表的仍用 \(int\) 。