Why doesn't int** ptr point to the same address as int arr[3][3] when accessing ptr[i][j]?
c++, pointers
Solution
`int **ptr` and an `int arr[3][3]` are different, since:
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| C | Maths |
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| ptr + 1 | ptr + sizeof(int*) |
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| arr + 1 | arr + 3 * sizeof(int*) |
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So you won't get the same results at all (moreover, `ptr` and `arr` may not have the same memory representation).
int (*ptr)[3] = arr;
will work, since only the first dimension of `arr` decays to a pointer.
Problem
I was answering this question but when I tested the following code I got confused. ``` #include <iostream> using namespace std; int main() { int **ptr; int arr[3][3]; ptr =(int **) arr; for (int i=0;i<3;i++){ for (int j=0;j<3;j++){ cout << &arr[i][j] << " =? "; cout << &(ptr[i][j]) << endl; } } return 0; } ``` But I get this ouput: ``` 0x7fff5700279c =? 0 0x7fff570027a0 =? 0x4 0x7fff570027a4 =? 0x8 0x7fff570027a8 =? 0 0x7fff570027ac =? 0x4 0x7fff570027b0 =? 0x8 0x7fff570027b4 =? 0 0x7fff570027b8 =? 0x4 0x7fff570027bc =? 0x8 ``` Why aren't they the same?