I am mis-understanding something about the code below. From my understanding the tester declaration should return a pointer to the first array of two elements, i.e. [1,2], and so *(tester+1) should return [3,4], which only has 2 elements so how does it make sense to call (*(tester + 1))[2] . This example prints the number 5 by the way. Any clarifications much appreciated.
int main() {
int tester[][2]{ 1,2,3,4,5,6 };
cout << (*(tester + 1))[2] << endl;
return 0;
}
When you declare a 2-dimensional array, all the elements are contiguous. The entire array is a single object, so you're not going out of bounds when you just exceed one of the row limits, so longer as you're still in the array. So the next element after tester[1,1] is tester[2,0], and that's what (*(tester + 1))[2] accesses.
[2] is higher than the highest element at [1] because the index starts at [0]
There are three arrays.
[1,2] positions 0,0 and 0,1
[3,4] positions 1,0 and 1,2
[5,6] positions 2,0 and 2,1
Since all of the arrays are next to each other in the data segment, going out of bounds on the second array (tester + 1) bleeds over into the third array giving you the first element of the third array. i.e. position 1,2 is the same as 2,0
int tester[][2]{ 1,2,3,4,5,6 } creates a 3 by 2 array.
tester[0][0] = 1
tester[0][1] = 2
tester[1][0] = 3
tester[1][1] = 4
tester[2][0] = 5
tester[2][1] = 6
The compiler creates an array using the least amount of memory possible based on your specifications. [][2] explicit says to organize the data in such a fashion that there a x rows and 2 columns. Because you put 6 elements into the tester array, the compiler decides the number of rows to assign by dividing the number of total elements by the number of columns.
Furthermore, (*(tester + 1))[2], is equivalent to tester[2], which would access the element in the first column of the third row. Thus returning 5.
It is another way to write this code which means you define vector but it acts like 2-dimensional array.
int main() {
int tester[3][2]{ {1,2},{3,4},{5,6} };
std::cout<< tester[1][2] <<std::endl;
return 0;
}
