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  1. // If you are not sure what some lines of code do, try looking back at
  2. // previous example programs, notes, or ask a question.
  3.  
  4. #include <iostream>
  5.  
  6. using namespace std;
  7.  
  8. int strlen(const char* str);
  9. int strcpy(char* dest, const char* src);
  10. char* getNewStr(int size);
  11.  
  12. int main() {
  13.  
  14. 	// Declaring an array on the stack vs. on the heap
  15. 	char stackStr[50];
  16. 	char* heapStr = new char[50];
  17.  
  18. 	// Both arrays can be used in the same ways
  19. 	for(int i = 0; i < 50; i++) {
  20. 		stackStr[i] = 'a';
  21. 		heapStr[i] = 'a';
  22. 	}
  23.  
  24. 	// However, the string on the heap must be deleted when
  25. 	// you are done with it--if you never deleted it is considered
  26. 	// leaked memory.
  27. 	delete[] heapStr;
  28. 	heapStr = NULL;
  29.  
  30. 	// Here, you can see how important is to delete your memory
  31. 	// before you lose access to it, or else this loop would
  32. 	// leak a ton of memory.
  33. 	for(int i = 0; i < 50; i++) {
  34. 		heapStr = new char[100];
  35.  
  36. 		// If the memory was not deleted, a new set of memory
  37. 		// would be assigned to "heapStr," and the previous
  38. 		// memory would be leaked.
  39. 		delete[] heapStr;
  40. 		heapStr = NULL;
  41. 	}
  42.  
  43. 	// Input a buffered string
  44. 	char buffer[100];
  45. 	cout << endl << "Enter a string: ";
  46. 	cin >> buffer;
  47.  
  48. 	// Allocate the exact number of characters necessary.
  49. 	heapStr = new char[strlen(buffer) + 1];
  50.  
  51. 	// Copy the string
  52. 	strcpy(heapStr,buffer);
  53.  
  54. 	cout << endl << "Exactly sized word: " << heapStr << endl << endl;
  55.  
  56. 	// Delete the string
  57. 	delete[] heapStr;
  58. 	heapStr = NULL;
  59.  
  60. 	// Finally, here is a function that will return dynamic memory.
  61. 	char* newStr = getNewStr(10);
  62.  
  63. 	// the memory originally created in the function can be deleted
  64. 	// here, at the end of main
  65. 	delete[] newStr;
  66.  
  67.  
  68. 	system("pause");
  69. 	return 0;
  70. }
  71.  
  72. char* getNewStr(int size) {
  73.  
  74. 	// Create a new dynamically allocated character array and return it.
  75. 	// The calling function will still have access to the memory, so it
  76. 	// does not need to be deleted here.
  77. 	return new char[size];
  78. }
  79.  
  80. int strlen(const char* str) {
  81. 	int counter = 0;
  82.  
  83. 	// Loop until you find a value that equals 0, the null char
  84. 	// (which marks the end of the string)
  85. 	while(str[counter])
  86. 		counter++;
  87.  
  88. 	return counter;
  89. }
  90.  
  91. int strcpy(char* dest, const char* src) {
  92.  
  93. 	int counter;
  94.  
  95. 	// Loop along the length of the source string,
  96. 	// and copy each character
  97. 	for(counter = 0; counter < strlen(src); counter++)
  98. 		dest[counter] = src[counter];
  99.  
  100. 	// Remember to add a null character at the end
  101. 	// of the destination string
  102. 	dest[counter] = '\0';
  103. }
  104.  
Success #stdin #stdout #stderr 0s 3472KB
comments (?)
stdin
copy 
hello!
stdout
copy 
Enter a string: 
Exactly sized word: hello!
stderr
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sh: 1: pause: not found
https://ideone.com/nxEwkD
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
secret

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