CT1M String Generator

CT1M String Generator.cpp

#include <iostream>
#include <string>
#include <limits>

std::string getPalindromeSum(int num) {
  if (1 == num) {
    return "0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + "
    + std::to_string(num) +
    " + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0";
  } else if ((num >= 2) && (num <= 10)) {
    num -= 2;
    return "0 + 0 + 0 + 0 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + "
    + std::to_string(num) +
    " + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0 + 0 + 0 + 0";
  } else if ((num >= 11) && (num <= 100)) {
    num -= 11;
    return "0 + 0 + 0 + 0 + 2.5 + 2 + 1 + "
    + std::to_string(num) +
    " + 1 + 2 + 2.5 + 0 + 0 + 0 + 0";
  } else if ((num >= 101) && (num <= 1'000)) {
    num -= 101;
    return "0 + 0 + 0 + 0 + 40.5 + 2 + 2 + 2 + 2 + 2 + "
    + std::to_string(num) +
    " + 2 + 2 + 2 + 2 + 2 + 40.5 + 0 + 0 + 0 + 0";
  } else if ((num >= 1'001) && (num <= 10'000)) {
    num -= 1'001;
    return "0 + 0 + 1 + 0 + 0 + 74.1 + 99.4 + 299 "
           "+ 1 + 26 + " + std::to_string(num) +
           " + 26 + 1 + 299 + 99.4 + 74.1 + 0 + 0 + 1 + 0 + 0";
  } else if ((num >= 10'001) && (num <= 50'000)) {
    num -= 9'974;
    return
      "0 + 0 + 0 + 0 + 1 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 999 +"
      " 999 + 999 + 333 + 333 + 0 + 0 + 0 + 222 + 37 + 37 + 30 + 7 + " +
      std::to_string(num) +
      " + 7 + 30 + 37 + 37 + 222 + 0 + 0 + 0 + 333 + 333 + 999 + 999 + 999 + 99 "
      "+ 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 1 + 0 + 0 + 0 + 0";
  } else if ((num >= 50'001) && (num <= 100'000)) {
    num -= 9'974;
    return
      "0 + 0 + 0 + 0 + 0 + 0 + 1 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 999 +"
      " 999 + 999 + 333 + 333 + 222 + 37 + 37 + 15 + 7 + 15 + " +
      std::to_string(num) +
      " + 15 + 7 + 15 + 37 + 37 + 222 + 333 + 333 + 999 + 999 + 999 + 99 "
      "+ 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 1 + 0 + 0 + 0 + 0 + 0 + 0";
  } else if ((num >= 100'001) && (num <= 500'000)) {
    num -= 9'974;
    return
      "0 + 0 + 0 + 0 + 1 + 23 + 0 + 1 + 75 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 999 +"
      " 999 + 999 + 333 + 333 + 222 + 37 + 37 + 30 + 7 + " +
      std::to_string(num) +
      " + 7 + 30 + 37 + 37 + 222 + 333 + 333 + 999 + 999 + 999 + 99 "
      "+ 99 + 99 + 99 + 99 + 99 + 99 + 99 + 99 + 75 + 1 + 0 + 23 + 1 + 0 + 0 + 0 + 0";
  } else if ((num >= 500'001) && (num <= 1'000'000)) {
    num -= 100'001;
    return
      "0 + 0 + 0 + 0 + 0 + 0.5 + 14909 + 14909 + 6969 + 4693 + 850 + 850 + 1700 +"
      " 1700 + 1700 + 340 + 340 + 340 + 340 + 340 + 10 + 5 + 2.5 + 2.5 + " +
      std::to_string(num) +
      " + 2.5 + 2.5 + 5 + 10 + 340 + 340 + 340 + 340 + 340 + 1700 + 1700 + 1700 + 850 + 850 +"
      " 4693 + 6969 + 14909 + 14909 + 0.5 + 0 + 0 + 0 + 0 + 0";
  }
  return "Number must be between 1 and 1'000'000";
}

[[nodiscard]] bool isValidInput(const int num, const int minRange,
                                const int maxRange) {
  return ((num >= minRange) && (num <= maxRange));
}

[[nodiscard]] bool isPalindrome(int num) {
  int reversedNum = 0;
  const int originalNum = num;

  while (num > 0) {
    const int digit = num % 10;
    reversedNum = ((reversedNum * 10) + digit);
    num /= 10;
  }

  return (originalNum == reversedNum);
}

int main() {
  int input{};
  const int minRange = 1;
  const int maxRange = 1'000'000;

  std::cout << "Enter numbers between 1 and 1,000,000 until EOF:\n";

  while (std::cin >> input) {
    if ((!std::cin.fail()) && (::isValidInput(input, minRange, maxRange))) {

      if ((input >= 100) && (::isPalindrome(input))) {
        std::cout << input << " is palindrome :)" << '\n';
      }

      std::cout << input << " -> " << ::getPalindromeSum(input) << '\n';
    } else {
      std::cout << "Invalid input. Please enter a valid number between "
                << minRange << " and " << maxRange << ".\n";

      std::cin.clear();
      std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    }
  }

  if (std::cin.eof()) {
    std::cout << "EOF encountered. Exiting the program.\n";
  } else {
    std::cout << "An error occurred while reading input. "
                 "Exiting the program.\n";
  }

  return 0;
}

////Better C++ Discord Coding competition: CT1M String Generator

////Input(stdin): an integer in the range [1,1 000 000]
////Output(stdout): an expression that evaluates to the number and
/// can be recognized by the bot in ⁠count-to-a-million, while also
/// being a palindrome.(e.g. ⁠count-to-a-million⁠)
////Repeat the input/output loop until EOF is encountered. Inputs
/// are delimited by a single \n.
////Use either C++ or Python.
////Restrictions:
////C++ code:
////Must compile in g++ with -std=c++23 and -m64. Warnings are
/// allowed.
////Relying on g++-specific behavior when the standard says
/// something is "implementation-defined" is allowed.
////The program must be conforming.
////Language-independent restrictions:
////Must run in a reasonable amount of time(max. 5 seconds to
/// evaluate all of 1-1 000 000)
////Must NOT do I/O except for the required inputs and outputs.
////Must NOT intentionally lag/harm/abuse the host computer,
/// including but not limited to: spawning other processes,
/// using too many threads, creating popups, creating a virus,
/// using system calls.
////Must use less than 4GB of RAM.
////Ranking:
////The program will be run with all numbers from 1 to one
/// million(inclusive). Programs are sorted by their average
/// output length over all inputs(shorter=better).
////Judge machine(mine): Windows 10 with MSYS2 Mingw64 G++
/// 13.1.0 and CPython 3.10.10
////Submissions are accepted until 8/1/2023 UTC.(MM/DD/YYYY)
//// Example input/output:
//// 696969 -> 0 + 0 + 0.5 + 14909 + 14909 + 6969 + 4693 +
/// 850 + 850 + 1700 + 1700 + 1700 + 1700 + 10 + 5 + 2.5 +
/// 2.5 + 596968 + 2.5 + 2.5 + 5 + 10 + 1700 + 1700 + 1700
/// + 1700 + 850 + 850 + 4693 + 6969 + 14909 + 14909 + 0.5 + 0 + 0
////Outputs must be on individual lines as well.