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  1. #include <iostream>
  2. #include <cstring>
  3.  
  4. using namespace std;
  5.  
  6. struct mynode{
  7. //some data
  8. mynode *left , *right;
  9. mynode(): left(NULL), right(NULL) {};				// Method 1
  10. };
  11.  
  12. int main(int argc, char* argv[])
  13. {
  14. 	int n = 5;
  15. 	int m = 10;
  16. 	mynode** p = new mynode*[n];					// Heap memory
  17.  
  18. 	// Or memset(p, (int)NULL, n * sizeof(mynode*));
  19. 	for(int i = 0; i < n; ++i)
  20. 	{
  21. 		p[i] = NULL;
  22. 	}	
  23.  
  24. 	for(int i = 0; i < n; ++i)
  25. 	{
  26. 		p[i] = new mynode[m];						// Heap memory
  27. 		memset(p[i], (int)NULL, m * sizeof(mynode));// Method 2, include <cstring> or <string.h>
  28. 		printf("left=%p, right=%p\n", p[i][0].left, p[i][0].right);
  29. 		// p[i] = &n;								// This case don't use delete [] p[i]. (Pointer to a variable)
  30. 	}
  31.  
  32. 	/*** do something ***/
  33.  
  34. 	for(int i = 0; i < n; ++i)
  35. 	{
  36. 		delete [] p[i];
  37. 	}
  38. 	delete [] p;
  39.  
  40. 	return 0;
  41. }
Success #stdin #stdout 0s 3272KB
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Standard input is empty
stdout
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left=(nil), right=(nil)
left=(nil), right=(nil)
left=(nil), right=(nil)
left=(nil), right=(nil)
left=(nil), right=(nil)
https://ideone.com/eK5wD0
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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