teratail_425361_answer_cpp_version_code

#include <iostream>
#include <optional>
#include <cstdint>
#include <vector>
#include <string>
#include <fstream>
#include <sstream>
#include <cassert>
#if __has_include(<format>)
#   include <format>
using std::format;
#elif __has_include(<fmt/core.h>)
#   include <fmt/core.h>
using fmt::format;
#else
#   error "not format function found."
#endif

struct data_t {
    uint64_t individual_number;
    std::string name;
    double height;
    double weight;
    std::optional<double> bmi;
    void calc_bmi();
    void debug_print() const;
    void print(std::ostream& os) const;
};
constexpr std::size_t init_line_buf_length = 512;
constexpr std::size_t init_vec_length = 256;
std::vector<data_t> data_read_from_file(const char* file_name)
{
#ifdef EXEC_ON_GODBOLT
    std::istream& in = std::cin;
#else
    std::ifstream in(file_name);
    if (!in) {
        std::cerr << "In function data_read_from_file:\nFail to open " << file_name << std::endl;
        return {};
    }
#endif
    std::vector<data_t> result_v;
    result_v.reserve(init_vec_length);
    // 動的メモリ確保は遅いのでループの外で行う
    std::string buf;
    buf.reserve(init_line_buf_length);
    while (std::getline(in, buf)) {
        data_t re = {};
        std::istringstream ss(buf);
        ss >> re.individual_number >> re.name >> re.height >> re.weight;
        result_v.emplace_back(std::move(re));
    }
    return result_v;
}
void data_t::calc_bmi()
{
    this->bmi = this->weight * 10000.0 / (this->height * this->height);
}
void data_t::debug_print() const
{
    std::cout << format("{0}     {1:8}     {2:.1f}    {3:.1f}", this->individual_number, this->name, this->height, this->weight) << std::endl;
    //printf("%" PRIu64 "     %-8s     %.1lf    %.1lf\n", this->individual_number, this->name, this->height, this->weight);
}
void data_t::print(std::ostream& os) const
{
    os << format("{0} {1:8} {2:.1f} {3:.1f}", this->individual_number, this->name, this->height, this->weight);
    //fprintf(stream, "%" PRIu64 " %-8s %.1lf %.1lf", d->individual_number, d->name, d->height, d->weight);
    if (this->bmi) {
        os << format(" {0:.1f}", *this->bmi) << std::endl;
        //fprintf(stream, " %.1lf\n", d->bmi.d);
    }
    else {
        os << " none" << std::endl;
        //fputs(" none\n", stream);
    }
}
int main(void)
{
    auto data = data_read_from_file("R7_in.txt");
    if (data.empty()) {
        return 2;
    }
    std::cout << "ID    NAME     HIGHT[cm]     WEIGHT[kg]" << std::endl;
    for (const auto& d : data) {
        d.debug_print();
        assert(!d.bmi.has_value());
    }
    for (auto&& d : data) {
        d.calc_bmi();
        assert(d.bmi.has_value());
    }
    std::sort(data.begin(), data.end(), [](const data_t& l, const data_t& r){ return l.bmi < r.bmi; });

#ifdef EXEC_ON_GODBOLT
    std::cout << "---" << std::endl;
#else
    std::ofstream out("R7_out.txt");
    if (out) {
        std::cerr << "In function main:\nFail to open R7_out.txt" << std::endl;
        return 2;
    }
#endif
    for (const auto& d : data) {
#ifdef EXEC_ON_GODBOLT
        d.print(std::cout);
#else
        d.print(out);
#endif
    }
    return 0;
}