What is the correct way to delete char**
I have a char**, basically an array of strings, that I need to delete. What is the correct way of doing this to ensure all pointer开发者_开发技巧s are cleared up?
The rule of thumb is that you need one delete
(or delete[]
) for each new
(or new[]
) that you issued.
So if you did:
char **pp = new char*[N];
for (i = 0; i < N; i++)
{
pp[i] = new char[L];
}
then you will need to clean up with:
for (i = 0; i < N; i++)
{
delete [] pp[i];
}
delete [] pp;
However, it should be noted that as you are in C++, you should probably be using std::vector<std::string>
rather than arrays of arrays of raw char
, because it would manage its own clean-up.
char** StringList ;
int nStrings ;
....
for (int i = 0 ; i < nStrings ; i++)
delete[] StringList[i] ;
delete[] StringList ;
Of course, it's simpler if you start with
std::vector<std::string> Stringlist ;
Then it's just
StringList.clear() ;
Do pattern matching as described below :
char *arr = new char[10];
char *p = new char;
delete [] arr;
delete p;
Did you see the pattern when to use what?
So now go to the original question:
char **dp = new char*[100]; //100 number of `char*`
for ( int i = 0 ; i < 100 ; i++ ) //loop for 100 times
dp[i] = new char[30]; //allocate memory for each `char*`
//deallocate
for ( int i = 0 ; i < 100 ; i++ )
delete [] dp[i]; //deallocate memory for each `char*`
delete [] dp; //deallocate memory for `char**`
for(int i = 0; i < array_length; ++i)
{
delete[] array[i]; // delete each entry in the array (assuming you used new[] for each string)
}
delete[] array; // delete the actual array.
I assume that you have array like this:
char **pp = new char* [10]; // for the base pointer
for(int i = 0; i < 10; i++)
pp[i] = new char[100]; // for every char* string
You should follow the reverse order. First clean up the member strings and then main pointer.
for(int i = 0; i < 10; i++)
delete[] pp[i];
delete[] pp;
for (int i = rows; i > 0; --i) {
delete[] anArray[i-1];
}
delete[] anArray;
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