Initializing a two-dimensional dynamic array
I am trying to initialize all the elements of a two-dimensional array when declaring it:
int** ints = new int* [n] { new int[n] { 0 } };
When trying to output the elements
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
cout << "i = " << i << "; j = " << j << "; value = " << ints[i][j] << endl;
I get this result in the console:
i = 0; j = 0; value = 0
i = 0; j = 1; value = 0
i = 0; j = 2; value = 0
i = 1; j = 0; value =
An exception is raised: нарушение прав доступа при чтении по адресу 0x0000000000000000.
I can't figure out what's going on.
n = 3.
When outputting elements of a one-dimensional array initialized in this way:
int* ints = new int[5];
The console displays
-842150451
-842150451
-842150451
-842150451
-842150451
, and such:
int* ints = new int[5] { 0 };
-
0
0
0
0
0
.
1 answers
When initializing an array with the specified size, the missing initializers are zeros. I.e.
int a[5] = {6};
Fills the array a with the values 6,0,0,0,0.
Note-initialization by value, not by expression evaluation :)
int i = 0;
int a[5] = {i++};
Will not apply i++ to all array elements.
What does
new int* [n] { new int[n] { 0 } };
? The single value new int[n] { 0 } is calculated and assigned to the first element of the array. The rest are filled in with zeros. Is the rest clear? :)
If you want to use exactly C++, and not some mutated C, then vector is in your hands:
vector<vector<int>> ints(n, vector<int>(n,0));
And no worries with freeing up memory :)
Update
On an extended question - in the complete absence of an initializer as such, no initialization is performed, and the array is filled with garbage as a result.