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  1. #include <iostream>
  2. #include <string.h>
  3.  
  4. class MyVector {
  5. private:
  6.     int *_pbegin;
  7.     int *_pend;
  8.     int *_pcapacity;
  9. public:
  10.     MyVector() {
  11.         _pbegin = new int;
  12.         _pend = _pbegin;
  13.         _pcapacity = _pbegin + 1;
  14.     }
  15.  
  16.     ~MyVector() {
  17.         delete _pbegin;
  18.     }
  19.  
  20. 	void reallocate(size_t newCapacity) {
  21. 		// Copy data into a temporary buffer
  22. 		size_t prevSize = size();
  23. 		int *prevData = new int[prevSize];
  24. 		memcpy(prevData, _pbegin, prevSize * sizeof(int));
  25.  
  26. 		// Remove current data from memory and
  27. 		// reallocate the amount of available memory
  28. 		delete _pbegin;
  29. 		_pbegin = new int[newCapacity];
  30. 		_pend = _pbegin + prevSize;
  31. 		_pcapacity = _pbegin + newCapacity;
  32.  
  33. 		//Copy previous data into the new memory
  34. 		memcpy(_pbegin, prevData, prevSize * sizeof(int));
  35.  
  36. 		// Remove the temporary buffer from memory
  37. 		delete prevData;
  38. 	}
  39.  
  40. 	void push(int value) {
  41. 		if (_pend == _pcapacity) {
  42. 			reallocate(capacity() * 2);
  43. 		}
  44.  
  45. 		*_pend = value;
  46. 		_pend++;
  47. 	}
  48.  
  49. 	int at(size_t pos) {
  50. 		return _pbegin[pos];
  51. 	}
  52.  
  53. 	size_t size() {
  54. 		return _pend - _pbegin;
  55. 	}
  56.  
  57. 	size_t capacity() {
  58. 		return _pcapacity - _pbegin;
  59. 	}
  60. };
  61.  
  62. int main() {
  63.     MyVector vec;
  64.  
  65. 	std::cout << "Current size: " << vec.size() << std::endl;
  66. 	std::cout << "Current capacity: " << vec.capacity() << std::endl << std::endl;
  67.  
  68. 	vec.push(42);
  69.  
  70. 	std::cout << "Inserted one element..." << std::endl;
  71. 	std::cout << "Current size: " << vec.size() << std::endl;
  72. 	std::cout << "Current capacity: " << vec.capacity() << std::endl << std::endl;
  73.  
  74. 	vec.push(1234);
  75.  
  76. 	std::cout << "Inserted one element..." << std::endl;
  77. 	std::cout << "Current size: " << vec.size() << std::endl;
  78. 	std::cout << "Current capacity: " << vec.capacity() << std::endl << std::endl;
  79.  
  80. 	vec.push(99);
  81.  
  82. 	std::cout << "Inserted one element..." << std::endl;
  83. 	std::cout << "Current size: " << vec.size() << std::endl;
  84. 	std::cout << "Current capacity: " << vec.capacity() << std::endl << std::endl;
  85.  
  86. 	vec.push(1);
  87. 	vec.push(500);
  88.  
  89. 	std::cout << "Inserted two elements..." << std::endl;
  90. 	std::cout << "Current size: " << vec.size() << std::endl;
  91. 	std::cout << "Current capacity: " << vec.capacity() << std::endl << std::endl;
  92.  
  93. 	std::cout << "Listing each element..." << std::endl;
  94. 	for (size_t i = 0; i < vec.size(); ++i) {
  95. 		printf("vec[%u] => %d\n", i, vec.at(i));
  96. 	}
  97. 	std::cout << std::endl;
  98. }
Success #stdin #stdout 0s 3428KB
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stdin
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Standard input is empty
stdout
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Current size: 0
Current capacity: 1

Inserted one element...
Current size: 1
Current capacity: 1

Inserted one element...
Current size: 2
Current capacity: 2

Inserted one element...
Current size: 3
Current capacity: 4

Inserted two elements...
Current size: 5
Current capacity: 8

Listing each element...
vec[0] => 42
vec[1] => 1234
vec[2] => 99
vec[3] => 1
vec[4] => 500
https://ideone.com/PhBxMm
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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