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  1. #include <iostream>
  2. #include <vector>
  3. #include <string>
  4. #include <sstream>
  5. using namespace std;
  6.  
  7. enum class ElemType
  8. {
  9. 	VAL, 
  10. 	DOWN, 
  11. 	UP, 
  12. 	NONE
  13. }; 
  14.  
  15. template <typename T>
  16. class Elem
  17. {
  18. 	public: 
  19. 	Elem(): t(ElemType::VAL), val(0) {}
  20. 	Elem(const ElemType _t, const T _val): t(_t), val(_val) {}
  21. 	Elem(const ElemType _t) : Elem(_t, 0) {}
  22.  
  23. 	ElemType t; 
  24. 	T val; 
  25. }; 
  26.  
  27.  
  28. template <typename T=int>
  29. class MyDS
  30. {
  31. 	public: 
  32. 	// Initialization Example: [1,2],3,[4,5],[], [6]
  33. 	MyDS(): v({{ElemType::DOWN}, {ElemType::VAL,1}, {ElemType::VAL,2}, {ElemType::UP}, {ElemType::VAL,3}, {ElemType::DOWN}, {ElemType::VAL,4}, {ElemType::VAL,5}, {ElemType::UP}, {ElemType::DOWN}, {ElemType::NONE}, {ElemType::UP}, {ElemType::DOWN}, {ElemType::VAL,6}, {ElemType::UP}}) {}
  34.  
  35. 	vector< Elem<T> > v;
  36.  
  37. 	string toStr() const 
  38. 	{
  39. 		stringstream res; 
  40. 		unsigned int curr_depth=0; 
  41.  
  42. 		bool isComma=false; 
  43. 		for(const auto& e : v)
  44. 		{
  45. 			if(e.t == ElemType::DOWN) {res << (isComma?",":"") << "["; isComma=false;} 
  46. 			else if(e.t == ElemType::UP) {res << "]"; isComma=true; }
  47. 			else if(e.t == ElemType::VAL) {res << ( (isComma)?",":"" ) << e.val; isComma=true;} 
  48. 			else if(e.t == ElemType::NONE) {res << ""; isComma=true;} 
  49. 		}
  50.  
  51. 		return res.str(); 
  52. 	}
  53. }; 
  54.  
  55. template <typename T>
  56. class MaybeMonad
  57. {
  58. 	public: 
  59. 	MaybeMonad(const T& _data): isValid(true), data(_data) {}
  60. 	MaybeMonad() : isValid(false), data(0) {}
  61.  
  62. 	const bool isValid; 
  63. 	const T data; 
  64.  
  65. 	string toStr() const 
  66. 	{
  67. 		if(isValid) return to_string(data); 
  68. 		return ""; 
  69. 	}
  70. }; 
  71.  
  72.  
  73.  
  74. template <typename T=int>
  75. class Iterator
  76. {
  77. 	public: 
  78. 	Iterator(const MyDS<T>& _d) : d(_d), index(0), n_vals(0), tot_n_vals(count()) {}
  79.  
  80. 	bool hasNext() const
  81. 	{
  82. 		return n_vals<tot_n_vals; 
  83. 	}
  84.  
  85. 	MaybeMonad<T> get()  
  86. 	{
  87. 		//MaybeMonad<T> res; 
  88. 		if(!is_index_valid) {is_index_valid=true; index=0;}
  89. 		else index++; 
  90. 		if(index == d.v.size()) throw runtime_error("No more elements"); 
  91. 		while( (d.v[index].t != ElemType::VAL) && (d.v[index].t != ElemType::NONE ) )
  92. 		{
  93. 			index++; 
  94. 			if(index == d.v.size()) throw runtime_error("No more elements"); 
  95. 		}
  96.  
  97. 		n_vals++; 		
  98. 		if(d.v[index].t == ElemType::VAL) return MaybeMonad<T>(d.v[index].val); 
  99. 		index++; 
  100. 		return MaybeMonad<T>(); 
  101. 	}
  102.  
  103. 	private: 
  104.  
  105. 	// Just get the reference, do not copy it 
  106. 	const MyDS<T>& d; 
  107.  
  108. 	bool is_index_valid; 
  109. 	unsigned int index; 
  110. 	unsigned int n_vals; 
  111. 	unsigned int tot_n_vals; 
  112.  
  113. 	// O(N) loop to count the actual elements 
  114. 	unsigned int count() const 
  115. 	{
  116. 		unsigned int res=0; 
  117. 		for(const auto& e : d.v) res += ( (e.t == ElemType::VAL) || (e.t == ElemType::NONE) )?1:0; 
  118. 		return res; 
  119. 	}
  120. }; 
  121.  
  122. int main() {
  123. 	// your code goes here
  124. 	MyDS<> d; 
  125. 	cout << d.toStr() << endl; 
  126. 	Iterator<> it(d); 
  127. 	while(it.hasNext()) cout << it.get().toStr() << ","; 
  128. 	cout << endl; 
  129. 	return 0;
  130. }
  131.  
  132.  
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  134.  
  135.  
  136.  
  137.  
  138.  
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  140.  
  141.  
  142.  
  143.  
  144.  
Success #stdin #stdout 0s 4436KB
comments (?)
stdin 
Standard input is empty
stdout 
[1,2],3,[4,5],[],[6]
1,2,3,4,5,,6,
https://ideone.com/n1Zuom
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
secret

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