I have an array within an array, for example:

```
[ 
    [0, 20, 5], 
    [5, 0, 15], 
    [5, 10, 0]
]

```

I need to get the max number in each column.

* The max of `[0 , 5 , 5]` is `5`, so that goes into the result array.
* The max of `[20, 0, 10]` is `20`, so that goes into the result array.
* The max of `[5, 15, 0]` is `15`, so that goes into the result array.

The final result array must contain `[5, 20, 15]`.