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Discussion on: Project Euler #4 - Largest Palindrome Product

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Ismail Bello

a lazy c++ solution :)

auto larget_palindrome_product(size_t n_digits) -> size_t {

    const auto is_palidrome = [](size_t x) -> bool {
        const auto as_string = std::to_string(x);
        auto fst = as_string.begin();
        auto lst = as_string.rbegin();
        for (; fst != as_string.end(); fst++, lst++)
            if (*fst != *lst) return false;
        return true;
    };

    size_t result = 0;
    const auto lower_bound = std::pow(10, n_digits - 1);
    const auto upper_bound = std::pow(10, n_digits) - 1;

    for (size_t fst = lower_bound; fst <= upper_bound; fst++) {
        for (size_t snd = fst; snd <= upper_bound; snd++) {
            if (auto n = fst * snd;
                is_palidrome(n) && n > result) {
                result = fst * snd;
            }
        }
    }

    return result;
}