Roman numerals
(Mylib/Misc/roman_numerals.cpp)

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• Last update: 2021-04-23 23:44:44+09:00

Operations

Requirements

Notes

Problems

References

Code

#pragma once
#include <string>

namespace haar_lib::misn {
  int roman_to_num(std::string s) {
    int ret = 0;

    for (int i = 0; i < (int) s.size(); ++i) {
      switch (s[i]) {
        case 'I': {
          if (i + 1 < (int) s.size() and (s[i + 1] == 'V' or s[i + 1] == 'X')) {
            ret -= 1;
          } else {
            ret += 1;
          }
          break;
        }

        case 'V': ret += 5; break;

        case 'X': {
          if (i + 1 < (int) s.size() and (s[i + 1] == 'L' or s[i + 1] == 'C')) {
            ret -= 10;
          } else {
            ret += 10;
          }
          break;
        }

        case 'L': ret += 50; break;

        case 'C': {
          if (i + 1 < (int) s.size() and (s[i + 1] == 'D' or s[i + 1] == 'M')) {
            ret -= 100;
          } else {
            ret += 100;
          }
          break;
        }

        case 'D': ret += 500; break;

        case 'M': ret += 1000; break;
      }
    }

    return ret;
  }

  std::string num_to_roman(int n) {
    std::string ret = "";

    if (n >= 1000) {
      int k = n / 1000;
      ret += std::string(k, 'M');
      n %= 1000;
    }

    if (n >= 100) {
      int k = n / 100;
      if (k <= 3)
        ret += std::string(k, 'C');
      else if (k == 4)
        ret += "CD";
      else if (k <= 8)
        ret += "D" + std::string(k - 5, 'C');
      else
        ret += "CM";

      n %= 100;
    }

    if (n >= 10) {
      int k = n / 10;
      if (k <= 3)
        ret += std::string(k, 'X');
      else if (k == 4)
        ret += "XL";
      else if (k <= 8)
        ret += "L" + std::string(k - 5, 'X');
      else
        ret += "XC";

      n %= 10;
    }

    int k = n;
    if (k <= 3)
      ret += std::string(k, 'I');
    else if (k == 4)
      ret += "IV";
    else if (k <= 8)
      ret += "V" + std::string(k - 5, 'I');
    else
      ret += "IX";

    return ret;
  }
}  // namespace haar_lib::misn

#line 2 "Mylib/Misc/roman_numerals.cpp"
#include <string>

namespace haar_lib::misn {
  int roman_to_num(std::string s) {
    int ret = 0;

    for (int i = 0; i < (int) s.size(); ++i) {
      switch (s[i]) {
        case 'I': {
          if (i + 1 < (int) s.size() and (s[i + 1] == 'V' or s[i + 1] == 'X')) {
            ret -= 1;
          } else {
            ret += 1;
          }
          break;
        }

        case 'V': ret += 5; break;

        case 'X': {
          if (i + 1 < (int) s.size() and (s[i + 1] == 'L' or s[i + 1] == 'C')) {
            ret -= 10;
          } else {
            ret += 10;
          }
          break;
        }

        case 'L': ret += 50; break;

        case 'C': {
          if (i + 1 < (int) s.size() and (s[i + 1] == 'D' or s[i + 1] == 'M')) {
            ret -= 100;
          } else {
            ret += 100;
          }
          break;
        }

        case 'D': ret += 500; break;

        case 'M': ret += 1000; break;
      }
    }

    return ret;
  }

  std::string num_to_roman(int n) {
    std::string ret = "";

    if (n >= 1000) {
      int k = n / 1000;
      ret += std::string(k, 'M');
      n %= 1000;
    }

    if (n >= 100) {
      int k = n / 100;
      if (k <= 3)
        ret += std::string(k, 'C');
      else if (k == 4)
        ret += "CD";
      else if (k <= 8)
        ret += "D" + std::string(k - 5, 'C');
      else
        ret += "CM";

      n %= 100;
    }

    if (n >= 10) {
      int k = n / 10;
      if (k <= 3)
        ret += std::string(k, 'X');
      else if (k == 4)
        ret += "XL";
      else if (k <= 8)
        ret += "L" + std::string(k - 5, 'X');
      else
        ret += "XC";

      n %= 10;
    }

    int k = n;
    if (k <= 3)
      ret += std::string(k, 'I');
    else if (k == 4)
      ret += "IV";
    else if (k <= 8)
      ret += "V" + std::string(k - 5, 'I');
    else
      ret += "IX";

    return ret;
  }
}  // namespace haar_lib::misn

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