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  1. #include <cassert>
  2. #include <initializer_list>
  3. #include <iostream>
  4. #include <string>
  5. #include <utility>
  6. #include <vector>
  7.  
  8. using namespace std;
  9.  
  10. int fromRoman(const string& x) {
  11.     auto first = crbegin(x);
  12.     const auto last = crend(x);
  13.  
  14.     auto decimalDigitFromRoman = [&](char unit, char five, char ten) {
  15.         int num = 0;
  16.         for (; first != last && *first == unit; ++first) ++num;
  17.         while (first != last && (*first == ten || *first == five)) {
  18.             num += *first == ten ? 10 : 5;
  19.             for (++first; first != last && *first == unit; ++first) --num;
  20.         }
  21.         return num;
  22.     };
  23.  
  24.     int num = 0, pow = 1;
  25.     for (auto syms : {"IVX", "XLC", "CDM"}) {
  26.         num += decimalDigitFromRoman(syms[0], syms[1], syms[2]) * pow;
  27.         pow *= 10;
  28.     }
  29.  
  30.     return num;
  31. }
  32.  
  33. int main() {
  34.     vector<pair<string, int>> testRomans{
  35.         {"I", 1},      {"II", 2},     {"III", 3},        {"IV", 4},         {"V", 5},
  36.         {"VI", 6},     {"VII", 7},    {"VIII", 8},       {"IX", 9},         {"X", 10},
  37.         {"XI", 11},    {"XII", 12},   {"XIII", 13},      {"XIV", 14},       {"XV", 15},
  38.         {"XVI", 16},   {"XVII", 17},  {"XVIII", 18},     {"XIX", 19},       {"XX", 20},
  39.         {"XXI", 21},   {"XXII", 22},  {"XXIII", 23},     {"XXIV", 24},      {"XXV", 25},
  40.         {"XXVI", 26},  {"XXVII", 27}, {"XXVIII", 28},    {"XXIX", 29},      {"XXX", 30},
  41.         {"XL", 40},    {"L", 50},     {"LIX", 59},       {"LX", 60},        {"LXIV", 64},
  42.         {"XCIX", 99},  {"C", 100},    {"MCMXCIX", 1999}, {"MMXIV", 2014},   {"IIII", 4},
  43.         {"VIIII", 9},  {"XIIX", 18},  {"XIIIII", 15},    {"MDCCCCX", 1910}, {"MDCDIII", 1903},
  44.         {"XXXXXX", 60}};
  45.  
  46.     for (const auto& x : testRomans) {
  47.         auto num = fromRoman(x.first);
  48.         assert(num == x.second);
  49.         cout << num << ", ";
  50.     }
  51.     cout << endl;
  52. }
  53.  
Success #stdin #stdout 0s 3460KB
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stdin
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Standard input is empty
stdout
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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 40, 50, 59, 60, 64, 99, 100, 1999, 2014, 4, 9, 18, 15, 1910, 1903, 60,
https://ideone.com/mhHldk
Roman Numeral to integer conversion routine.
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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