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  1. #include<iostream>
  2. #include<type_traits>
  3.  
  4. int constexpr powOf10(size_t power)
  5. {
  6.     return power == 0 ? 1 : 10 * powOf10(power - 1);
  7. }
  8.  
  9. template<int... digits>
  10. struct buildNumber;
  11.  
  12. template<int first, int... digits>
  13. struct buildNumber<first, digits...> : std::integral_constant<int, first * powOf10(sizeof...(digits)) + buildNumber<digits...>::value>
  14. {
  15. };
  16.  
  17. template<>
  18. struct buildNumber<> : std::integral_constant<int, 0>
  19. {
  20. };
  21.  
  22. template<int... digits>
  23. struct areAllDigits;
  24.  
  25. template<int first, int... digits>
  26. struct areAllDigits<first, digits...>
  27. {
  28.     static bool constexpr value = first > 0 && first < 10 && areAllDigits<digits...>::value;
  29. };
  30.  
  31. template<int first>
  32. struct areAllDigits<first>
  33. {
  34.     static bool constexpr value = first>0 && first < 10;
  35. };
  36.  
  37. template<class T>
  38. struct buildNumberT;
  39.  
  40.  
  41. template<int... digits>
  42. struct digitContainer
  43. {
  44.  
  45. };
  46.  
  47.  
  48. template<int... digits>
  49. struct buildNumberT<digitContainer<digits...>> : buildNumber<digits...> {};
  50.  
  51. template<class T1, class T2>
  52. struct concatCtr;
  53.  
  54. template<int... digits1, int... digits2>
  55. struct concatCtr<digitContainer<digits1...>, digitContainer<digits2...>>
  56. {
  57.     typedef  digitContainer<digits1..., digits2...> type;
  58. };
  59.  
  60. template<int number, size_t digit>
  61. struct breakIntoDigits
  62. {
  63.     typedef typename concatCtr<digitContainer<number / powOf10(digit)>, typename breakIntoDigits<number % powOf10(digit), digit - 1>::ctr>::type ctr;
  64. };
  65.  
  66. template<int number>
  67. struct breakIntoDigits<number, 0>
  68. {
  69.     typedef digitContainer<number> ctr;
  70. };
  71.  
  72. template<int needle, int... haystack>
  73. struct contains;
  74.  
  75. template<int needle, int first, int... haystack>
  76. struct contains<needle, first, haystack...>
  77. {
  78.     static bool constexpr value = needle == first || contains<needle, haystack...>::value;
  79. };
  80.  
  81. template<int needle>
  82. struct contains<needle>
  83. {
  84.     static constexpr bool value = false;
  85. };
  86.  
  87. template<int... values>
  88. struct max;
  89.  
  90. template<int first, int... rest>
  91. struct max<first, rest...>
  92. {
  93.     static constexpr int value = first > max<rest...>::value ? first : max<rest...>::value;
  94. };
  95.  
  96. template<>
  97. struct max<>
  98. {
  99.     static int constexpr value = 0;
  100. };
  101.  
  102. template<class container, int... digits>
  103. struct ruleChecker;
  104.  
  105. template<int current, int... allPrevious, int... rest>
  106. struct ruleChecker<digitContainer<allPrevious...>, current, rest...>
  107. {
  108.     static bool constexpr value = (current == 0 || sizeof...(allPrevious) == 0 || contains<current, allPrevious...>::value || current > max<allPrevious...>::value) && ruleChecker<digitContainer<allPrevious..., current>, rest...>::value;
  109. };
  110.  
  111. template<class container>
  112. struct ruleChecker<container>
  113. {
  114.     static bool constexpr value = true;
  115. };
  116.  
  117. template<class ctr1, class ctr2>
  118. struct ruleCheckerT;
  119.  
  120. template<class ctr1, int... set2>
  121. struct ruleCheckerT<ctr1, digitContainer<set2...>> : ruleChecker<ctr1, set2...>{};
  122.  
  123.  
  124. template<int number, int length>
  125. struct isValidNumber : ruleCheckerT<digitContainer<>, typename breakIntoDigits<number, length>::ctr>
  126. {
  127. };
  128.  
  129.  
  130. template<int number, int length>
  131. struct generateList
  132. {
  133.     typedef typename std::conditional<number % powOf10(length) == 0, 
  134. 		digitContainer<>,
  135. 		typename concatCtr<
  136. 			typename generateList<number + 1, length>::container,
  137. 			typename std::conditional<isValidNumber<number, length>::value,
  138. 					digitContainer<number>,
  139. 					digitContainer<>
  140. 				>::type
  141. 			>::type
  142. 		>::type container;
  143. };
  144.  
  145. template<int number>
  146. struct generateList<number, 1>
  147. {
  148.     typedef typename concatCtr<
  149.     	typename generateList<number + 1, 1>::container,
  150.     	typename std::conditional<isValidNumber<number, 1>::value,
  151.     			digitContainer<number>,
  152.     			digitContainer<>
  153.     		>::type
  154.     	>::type container;
  155. };
  156.  
  157. #define DEFINE_ENDPOINT_FOR_LENGTH(length) template<> struct generateList<powOf10(length), (length)>{typedef digitContainer<> container;}
  158.  
  159. template<int length>
  160. struct insanity
  161. {
  162.     static_assert(length > 0, "Length must be greater than 0.");
  163.     typedef typename concatCtr<typename generateList<1, length>::container, digitContainer<0>>::type numberList;
  164. };
  165.  
  166. template<int first, int... rest>
  167. void outputContainer(digitContainer<first, rest...> values)
  168. {
  169. 	std::cout<<first<<'\n';
  170.     outputContainer(digitContainer<rest...>{});
  171. }
  172.  
  173. void outputContainer(digitContainer<> empty)
  174. {
  175.     std::flush(std::cout);
  176. }
  177. DEFINE_ENDPOINT_FOR_LENGTH(1);
  178. DEFINE_ENDPOINT_FOR_LENGTH(2);
  179. int main()
  180. {
  181.     outputContainer(insanity<2>::numberList{});
  182. }
Success #stdin #stdout 0s 2900KB
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https://ideone.com/D0sZrj
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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