How can I compare the columns elements in 2d array? - c++

Question

I have created a 2d array, so lets say as I did in the code below the array elements shows like this:
3 4
8 2
I want to compare the" ROWS" and get the minimum number, like what I do with 3 & 4, I get 3 is the min number and with the second row between 8 & 2, I get 2 is the min number.
My problem is that I can't get it to compare the columns as in 3 & 8 to get the max out between them, and 4 & 2.
In the code it just outputs the max number in the rows it still comparing the "ROWS"
P.S sorry for the long explanation. I just had to clarify it .
int main()
{
int d;
int max;
//array dimention
cout << "Enter the array dimention :- " << endl;
cin >> d;
//max_min for the final maximum numbers
int max_num[d];
//the 2d array
int arr[d][d];
// array input
cout << "please enter the array elements :- " << endl;
for (int i = 0; i < d; i++) {
for (int j = 0; j < d; j++) {
cin >> arr[i][j];
}
}
//array output
cout << "the array elements you enterd :-" << endl;
for (int i = 0; i < d; i++) {
for (int j = 0; j < d; j++) {
cout << arr[i][j] << " ";
}
cout << endl;
}
//the max numbers
for (int i = 0; i < d; i++) {
max = arr[0][i];
for (int j = 0; j < d; j++) {
if (max < arr[j][i]) {
max = arr[j][i];
}
}
max_num[i] = max;
}
cout << "the maximum elements in array :-" << endl;
for (int i = 0; i < d; i++) {
cout << max_num[i] << endl;
}
}