C++ – 快读与快写

#ifdef __cpp_if_constexpr

template <typename T, typename... Args>
void read(T& x, Args&... r) {
    if constexpr (is_integral_v<T> && !is_same_v<decay_t<T>, char>) {
        x = 0;
        lli f = 1;
        char ch = getchar();
        while (!isdigit(ch)) {
            if (ch == '-') f = -1;
            ch = getchar();
        }
        while (isdigit(ch)) {
            x = (x << 1) + (x << 3) + (ch ^ 48);
            ch = getchar();
        }
        x *= f;
    } else if constexpr (is_same_v<decay_t<T>, string>) {
        x.resize(buf);
        char* ptr = x.data();
        read(ptr);
        x.resize(strlen(x.data()));
    } else if constexpr (is_same_v<decay_t<T>, char*>) {
        scanf("%s", x);
    } else if constexpr (is_same_v<decay_t<T>, char>) {
        x = getchar();
        while (isspace(x)) x = getchar();
    } else cin >> x;
    if constexpr (sizeof...(r) > 0) read(r...);
}

#else

template<typename T>
void read(T& x) {
    cin >> x;
}

template <typename T, typename... Args>
void read(T& x, Args&... r) {
    read(x); read(r...);
}

#endif

template <typename T>
void read_vec(vector<T>& vec, lli n, lli offset = 1) {
    vec.resize(n + offset);
    for (lli i = offset; i < n + offset; ++i)
        read(vec[i]);
}

#define input(...)          lli __VA_ARGS__; read(__VA_ARGS__)
#define input_vec(vec, ...) vector<lli> vec; read_vec(vec, __VA_ARGS__)

#ifdef __cpp_if_constexpr

template <typename T, typename ...Args>
void write(const T& x, const Args&... r) {
    if constexpr (is_integral_v<T> && !is_same_v<decay_t<T>, char>) {
        lli y = x;
        if (y < 0) {
            putchar('-');
            y = -y;
        }
        if (y > 9) write(y / 10);
        putchar(y % 10 + '0');
    } else if constexpr (is_same_v<decay_t<T>, string>) {
        write(x.c_str());
    } else if constexpr (is_same_v<decay_t<T>, char*>) {
        fputs(x, stdout);
    } else if constexpr (is_same_v<decay_t<T>, char>) {
        putchar(x);
    } else if constexpr (is_same_v<decay_t<T>, bool>) {
        putchar(x ? 'T' : 'F');
    }
    else cout << x;
    if constexpr (sizeof...(r) > 0) write(r...);
}

#else

template<typename T>
void write(const T& x) {
    cout << x;
}

template <typename T, typename... Args>
void write(const T& x, const Args&... r) {
    write(x); write(r...);
}

#endif

template <typename T>
void write_vec(const vector<T>& vec, lli n, lli offset = 1) {
    for (lli i = offset; i < n + offset; ++i)
        write(vec[i], ' ');
    write('\n');
}

#ifdef _DEBUG
#   define debug(...)      write(__VA_ARGS__)
#   define debug_vec(...)  write_vec(__VA_ARGS__)
#   define debug_code(...) do __VA_ARGS__ while (false)
#else
#   define debug(...)
#   define debug_vec(...)
#   define debug_code(...)
#endif